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Objective: To determine the effect of mask use on viral respiratory infection risk. Data sources: MEDLINE and the Cochrane Library. Study selection: Randomized controlled trials (RCTs) included in at least 1 published systematic review comparing the use of masks with a control group, either in community or health care settings, on the risk of viral respiratory infections. Synthesis: In total, 11 systematic reviews were included and 18 RCTs of 26 444 participants were found, 12 in the community and 6 in health care workers. Included studies had limitations and were deemed at high risk of bias. Overall, the use of masks in the community did not reduce the risk of influenza, confirmed viral respiratory infection, influenzalike illness, or any clinical respiratory infection. However, in the 2 trials that most closely aligned with mask use in real-life community settings, there was a significant risk reduction in influenzalike illness (risk ratio [RR] = 0.83; 95% CI 0.69 to 0.99). The use of masks in households with a sick contact was not associated with a significant infection risk reduction in any analysis, no matter if masks were used by the sick individual, the healthy family members, or both. In health care workers, surgical masks were superior to cloth masks for preventing influenzalike illness (RR = 0.12; 95% CI 0.02 to 0.98), and N95 masks were likely superior to surgical masks for preventing influenzalike illness (RR = 0.78; 95% CI 0.61 to 1.00) and any clinical respiratory infections (RR = 0.95; 95% CI 0.90 to 1.00). Conclusion: This systematic review found limited evidence that the use of masks might reduce the risk of viral respiratory infections. In the community setting, a possible reduced risk of influenzalike illness was found among mask users. In health care workers, the results show no difference between N95 masks and surgical masks on the risk of confirmed influenza or other confirmed viral respiratory infections, although possible benefits from N95 masks were found for preventing influenzalike illness or other clinical respiratory infections. Surgical masks might be superior to cloth masks but data are limited to 1 trial.
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Editor’s key points
There is growing advocacy for the
use of masks in the community
to prevent transmission of viral
respiratory infections. This
systematic review found limited
evidence that the use of masks might
prevent viral respiratory infections.
The use of masks by a group in
the community setting appears to
reduce influenzalike illness in those
wearing masks. The pooled analysis
showed a significant risk reduction
(number needed to treat [NNT] = 24).
Using masks within a family 1 to 3
days after someone has developed
symptoms of a viral respiratory
infection does not appear to
prevent transmission to family
members, no matter if the masks
are used by the sick individual, the
healthy family members, or both.
Surgical masks are likely superior
to cloth masks for preventing
influenzalike illness in health care
workers (NNT = 50) but the results
are drawn from a single trial. N95
masks are likely superior to surgical
masks for preventing influenzalike
illness (NNT = 100) and clinical
respiratory infections (NNT = 40) in
health care workers.
Masks for prevention of
viral respiratory infections
among health care workers
and the public
PEER umbrella systematic review
Nicolas Dugré PharmD MSc Joey Ton PharmD Danielle Perry RN
Scott Garrison MD PhD CCFP Jamie Falk PharmD James McCormack PharmD
Samantha Moe PharmD Christina S. Korownyk MD CCFP
Adrienne J. Lindblad ACPR PharmD Michael R. Kolber MD CCFP MSc
Betsy Thomas BScPharm Anthony Train MB ChB MSc CCFP G. Michael Allan MD CCFP
Abstract
Objective To determine the effect of mask use on viral respiratory infection risk.
Data sources MEDLINE and the Cochrane Library.
Study selection Randomized controlled trials (RCTs) included in at least 1 published
systematic review comparing the use of masks with a control group, either in
community or health care settings, on the risk of viral respiratory infections.
Synthesis In total, 11 systematic reviews were included and 18 RCTs of 26 444
participants were found, 12 in the community and 6 in health care workers.
Included studies had limitations and were deemed at high risk of bias. Overall,
the use of masks in the community did not reduce the risk of influenza,
confirmed viral respiratory infection, influenzalike illness, or any clinical
respiratory infection. However, in the 2 trials that most closely aligned with
mask use in real-life community settings, there was a significant risk reduction
in influenzalike illness (risk ratio [RR] = 0.83; 95% CI 0.69 to 0.99). The use of
masks in households with a sick contact was not associated with a significant
infection risk reduction in any analysis, no matter if masks were used by the
sick individual, the healthy family members, or both. In health care workers,
surgical masks were superior to cloth masks for preventing influenzalike illness
(RR = 0.12; 95% CI 0.02 to 0.98), and N95 masks were likely superior to surgical
masks for preventing influenzalike illness (RR = 0.78; 95% CI 0.61 to 1.00) and any
clinical respiratory infections (RR = 0.95; 95% CI 0.90 to 1.00).
Conclusion This systematic review found limited evidence that the use of
masks might reduce the risk of viral respiratory infections. In the community
setting, a possible reduced risk of influenzalike illness was found among mask
users. In health care workers, the results show no difference between N95
masks and surgical masks on the risk of confirmed influenza or other confirmed
viral respiratory infections, although possible benefits from N95 masks were
found for preventing influenzalike illness or other clinical respiratory infections.
Surgical masks might be superior to cloth masks but data are limited to 1 trial.
510 Canadian Family Physician | Le Médecin de famille canadien Vol 66: JULY | JUILLET 2020
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Points de repère
du rédacteur
Le port du masque est de plus
en plus préconisé pour prévenir
la transmission des infections
respiratoires virales. Cette revue
systématique a trouvé un nombre
limité de données pour soutenir
que l’utilisation d’un masque
est susceptible de prévenir les
infections respiratoires virales.
Le port du masque par un groupe
dans un milieu communautaire
semble réduire les affections
pseudo-grippales chez les
personnes qui portent le masque.
L’analyse regroupée a démontré
une réduction significative du
risque (nombre de sujets à traiter
[NST] = 24). Porter un masque au
sein d’une famille de 1 à 3 jours
après que l’un des membres a
développé des symptômes d’une
infection respiratoire virale ne
semble pas prévenir la transmission
aux autres membres de la famille,
peu importe si le masque est porté
par la personne malade, par les
membres en santé de la famille ou
par tous.
Les masques chirurgicaux sont
probablement supérieurs aux
masques en tissu pour prévenir les
affections pseudo-grippales chez
les travailleurs de la santé
(NST = 50), mais ces résultats
proviennent d’un seul essai. Les
masques N95 sont probablement
supérieurs aux masques
chirurgicaux pour prévenir les
affections pseudo-grippales
(NST = 100) et les infections
respiratoires cliniques (NST = 40)
chez les travailleurs de la santé.
Les masques pour prévenir les
infections respiratoires virales
chez les travailleurs de la
santé et la population
Revue-cadre systématique du groupe PEER
Nicolas Dugré PharmD MSc Joey Ton PharmD Danielle Perry RN
Scott Garrison MD PhD CCFP Jamie Falk PharmD James McCormack PharmD
Samantha Moe PharmD Christina S. Korownyk MD CCFP
Adrienne J. Lindblad ACPR PharmD Michael R. Kolber MD CCFP MSc
Betsy Thomas BScPharm Anthony Train MB ChB MSc CCFP G. Michael Allan MD CCFP
Résumé
Objectif Déterminer les effets du port du masque sur le risque d’infections
respiratoires virales.
Sources des données MEDLINE et la Bibliothèque Cochrane.
Sélection des études Les essais contrôlés randomisés (ECR) inclus dans au moins 1
revue systématique publiée comparant le port du masque avec cette pratique dans
un groupe témoin, soit en milieu communautaire ou en milieu de soins de santé,
portant sur le risque d’infections respiratoires virales.
Synthèse Au total, 11 revues systématiques ont été incluses, et 18 ECR auprès de
26 444 participants ont été recensés, 12 dans la communauté et 6 chez des travailleurs
de la santé. Les études retenues comportaient certaines limites et étaient jugées à
risque élevé de biais. Dans l’ensemble, le port du masque dans la communauté n’a pas
réduit le risque de grippe, d’infections respiratoires virales confirmées, d’affections
pseudo-grippales ou de toute autre infection respiratoire clinique. Toutefois, dans 2
essais qui concordaient le plus étroitement avec le port du masque dans des milieux
communautaires de la vie réelle, il s’est produit une réduction significative du risque
d’affections pseudo-grippales (risque relatif [RR] = 0,83; IC à 95 de 0,69 à 0,99). Dans
les analyses, le port du masque dans les familles en contact avec un membre malade
n’était pas associé à une réduction significative du risque d’infection, que le masque
soit utilisé ou non par le mlde, pr les membres en snté de l fmille ou pr tous.
Chez les trvilleurs de la santé, les masques chirurgicaux étaient supérieurs aux
masques en tissu pour prévenir les affections pseudo-grippales (RR = 0,12; IC à 95 %
de 0,02 à 0,98), et les masques N95 étaient probablement supérieurs aux masques
chirurgicaux pour prévenir les affections pseudo-grippales (RR = 0,78; IC à 95 % de 0,61 à
1,00) et les autres infections respiratoires cliniques (RR = 0,95; IC à 95 % de 0,90 à 1,00).
Conclusion Cette revue systématique a dégagé des données probantes limitées selon
lesquelles le port du masque pourrait réduire le risque d’infections respiratoires
virales. Dans la communauté, une réduction possible du risque d’affections pseudo-
grippales a été observée chez les porteurs de masque. Chez les travailleurs de la santé,
les résultats n’ont démontré aucune différence entre les masques N95 et les masques
chirurgicaux quant au risque de grippe confirmée ou d’autres infections respiratoires
virales confirmées, quoique des bienfaits possibles puissent être attribués aux
masques N95 pour prévenir les affections pseudo-grippales ou d’autres infections
respiratoires cliniques. Les masques chirurgicaux pourraient être supérieurs aux
masques en tissu, mais les données proviennent de 1 seul essai.
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In the management of infectious disease, prevention
is clearly preferred to treatment. For viral respira-
tory infections, the list of preventive options includes
vaccines, physical distancing, isolation (of those who
are sick), quarantine (of those who are exposed), hand
hygiene, masks, and a host of other interventions. For
health care workers, masks are one part of personal
protective equipment (PPE), but the amount of PPE var-
ies based on the clinical environment, current risk level,
and local directives. As the coronavirus disease 2019
(COVID-19) pandemic continues to spread, so has advo-
cacy for public mask use, with rationale based on simple
precautionary principles and the potential for benefit
over harm.1,2
In observational studies, wearing masks is associated
with a lower risk of contracting viral respiratory infec-
tions.3,4 For example, in a 2011 Cochrane systematic
review published by Jefferson et al, the use of masks in
case-control studies was associated with an important
risk reduction (odds ratio = 0.32; 95% CI 0.26 to 0.39).3
However, the observational design is at high risk of con-
founding and mask use might simply be a surrogate
measure for comparing more careful versus less careful
people. Experimental laboratory-based studies of masks
and mask types seem to provide promising and impor-
tant information, but translation into meaningful clinical
differences is often lacking.5 To reduce confounding and
determine the true effects of masks on infection preven-
tion, randomized controlled trial (RCT) data are required.
While there are a number of recent systematic reviews
of RCTs, some meta-analyzed studies had differing
designs or settings, which led to increased heterogene-
ity, while others focused on a very specific question.6-9
Some meta-analyses also did not appear to account for
cluster-randomized designs.4,6,8
Trials are under way to determine if masks can
reduce the spread of COVID-19 (ClinicalTrials.gov:
NCT04296643 and NCT04337541); however, none were
published at the time of writing.10 This systematic review
examines if masks can reduce the risk of viral respira-
tory infections in members of the public or in health care
workers. In addition, this review will examine if the type
of mask influences the risk of viral respiratory infections.
Methods ——
We followed PRISMA (Preferred Reporting Items for
Systematic Reviews and Meta-Analyses) guidelines
for completion of this systematic review.11 Our search
was modified to improve efficiency, similar to our previ-
ous systematic reviews.12,13
Search
Two team members (J.T. and D.P.) performed a search
of MEDLINE via Ovid from inception to May 5, 2020.
This search was limited to systematic reviews and used
both key and MeSH terms related to masks and infec-
tious disease transmission. In addition to MEDLINE,
the search was carried out on the same date in the
Cochrane Library, using the same terminology and lim-
ited to Cochrane systematic reviews. A search for RCTs
published in MEDLINE or added to the MedRxiv preprint
database from January 1, 2020, to May 5, 2020, was also
performed to identify any new trials not captured by the
included systematic reviews. Full details of the search
strategy, including MeSH terms, are in Appendix 1, avail-
able from CFPlus.*
Study selection
For added efficiency, our modified approach involved
identifying systematic reviews of studies examining the
use of masks for the prevention of viral respiratory infec-
tions. Systematic reviews were included if they were
published in English and they reported at least 1 RCT
comparing any mask use, either alone or in combination
with other interventions, with a control group. Systematic
reviews were reviewed by 2 team members and disagree-
ments were resolved by consensus and consultation with
a third author when necessary. Once all relevant system-
atic reviews were located, RCTs from each were reviewed
and included if they studied mask use for the prevention
of viral respiratory infections, either in health care work-
ers or in people in the community. The same inclusion
criteria were applied to individual RCTs found in the addi-
tional search for RCTs that were published in 2020. We
excluded observational studies and laboratory or surro-
gate experimental studies.
Data extraction
Data extraction was performed by a single reviewer,
with a second author reviewing for accuracy. Extracted
data included country, setting, population enrolled,
population details (eg, age, sex), cluster details when
appropriate (eg, universities, schools, tents), number of
participants randomized, number of participants ana-
lyzed, duration of study, types of masks used, who was
directed to wear masks, direction on when to wear
masks (eg, all of the time, 5 hours per day), adherence to
mask use, and data on 4 outcomes (confirmed influenza,
any confirmed viral respiratory infection, influenzalike
illness, and any clinical respiratory infection).
Quality assessment
Risk of bias for each RCT was assessed by 2 reviewers
(N.D. and G.M.A.) using the Cochrane Collaboration risk-
of-bias assessment tool.14
*The full PRISMA flow diagram (Appendix ); forest plots for all
analyses (Appendix ); all original trial data, cluster sizes, intracluster
correlation coefficients, adjusted events, and sample sizes (Appendix
); and Table  and Figure  are available at www.cfp.ca. Go to the
full text of the article online and click on the CFPlus tab.
512 Canadian Family Physician | Le Médecin de famille canadien Vol 66: JULY | JUILLET 2020
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Analysis
We focused on 4 primary end points: confirmed influenza,
confirmed viral respiratory tract infection, influenzalike
illness (defined by RCT authors), and any clinical respira-
tory tract infection. For all RCTs, we extracted the num-
ber of events for each outcome when available and the
number of participants analyzed in both the interven-
tion group and the control group. In studies where the
participants were randomized individually, we applied
those values directly into our analysis. For cluster RCTs,
we adjusted those values to account for clustering by
dividing the numbers by the design effect, with the
design effect calculated using the following equation:
design effect = 1 + ([cluster size - 1] × ICC), where ICC is
the intracluster correlation coefficient.15 Cluster size was
calculated by dividing the number of patients by the
number of clusters. The ICC was identified in the trials
whenever possible: first, if the authors provided an ICC
they calculated for a specific outcome; or second, if the
authors provided an expected ICC when determining
sample size. If the trial did not provide an ICC, we used
the ICC estimate from a similar study. This approach
allowed all results to be analyzed in a similar fashion.
Meta-analyses were performed to calculate risk ratios
(RRs) by pooling adjusted events and numbers. When a
study had multiple arms used in the same analysis, we
divided the total number of participants in the control
group by the number of intervention groups to avoid
counting participants more than once. Subgroup analyses
were performed based on setting (community or clinical
setting), mask type, control group, and who wore masks
(eg, only sick people, only healthy people). Because simi-
lar designs and settings were pooled, fixed-effects models
were used. We also performed random-effects sensitivity
analyses in the comparisons of N95 and surgical masks,
as different approaches to wearing N95 masks were used
(such as fit-tested versus non–fit-tested masks, or masks
worn only for higher-risk clinical scenarios versus worn
all day). Absolute risks of events and numbers needed
to treat (NNTs) were calculated by pooling the unad-
justed event rates in the control groups (baseline risk)
and applying cluster-adjusted, meta-analyzed, relative-
effects estimates to attain absolute benefits.
Synthesis ——
The search found 544 publications, out of which 11 relevant
systematic reviews were identified. Three of these system-
atic reviews were published in 2020. Six systematic reviews
focused on the effect of masks on influenza incidence.
From these 11 systematic reviews, 18 unique RCTs
were identified, including a total of 26 444 participants.
No additional RCTs published in 2020 were found. The
full PRISMA flow diagram is available in Appendix 1.*
All 18 RCTs involved using masks to prevent the spread
of viral respiratory infections and were broken into
2 primary groups: community use (n = 12) and use by
health care workers (n = 6). Details of the RCTs con-
ducted in community settings are found in Table 1,16-27
available from CFPlus.* Details of the RCTs conducted
in health care settings are found in Table 2.28-33 All trials
were deemed at high risk of bias. Risk-of-bias assess-
ment for each RCT is available in Appendix 1.*
All primary results for both settings are available in
Table 3. Forest plots for all analyses are available
in Appendix 2 from CFPlus.* All original trial data, clus-
ter sizes, intracluster correlation coefficients, adjusted
events, and sample sizes are provided in Appendix 3
from CFPlus.*
Community setting
All 12 community trials were cluster RCTs. Nine of these
12 community RCTS involved an index case. In 7 of
those, the index case was identified after receiving a
diagnosis of influenza or influenzalike illness by a health
care professional.19,21-25,27 The patient’s family was then
subsequently enrolled in the trial. In the intervention
arms, mask use could be recommended for everyone,
just the sick person, just the healthy family members
at home, or both. In 1 RCT conducted during the Hajj
in Saudi Arabia, index cases were pilgrims presenting
with influenzalike illness and the enrolled contacts were
the individuals sleeping within 2 metres of an index
case in the accommodation tents.26 In the intervention
arm, both index cases and contacts had to wear masks.
In 1 trial, masks were given to 509 households in New
York, NY, and participants were told to start using masks
if 1 household member developed influenzalike illness
(masks for the ill person and the caretaker).20 In the
3 remaining trials, masks were used in a prespecified
healthy population group, either American university
students randomized by residence hall or Australian Hajj
pilgrims randomized by accommodation tent.16-18
The use of masks in community settings in general
did not reduce the risk of confirmed influenza (RR = 0.97;
95% CI 0.75 to 1.25; I2 = 0%) or confirmed viral respiratory
infection (RR = 1.28; 95% CI 0.87 to 1.89; I2 = 0%). Results
were not statistically significant in any subgroup analy-
sis (masks worn by all, just the sick person, or just the
healthy family members at home). The use of masks in
community settings did not result in a significant risk
reduction of influenzalike illness (RR = 0.91; 95% CI 0.80 to
1.03; I2 = 0%) or any clinical respiratory infection (RR = 1.06;
95% CI 0.82 to 1.36; I2 = 0%). However, for influenzalike ill-
ness, the use of masks by everyone for 6 weeks during
influenza season in 2 RCTs conducted in an American
university appeared to reduce risk (RR = 0.83; 95% CI 0.69
to 0.99; I2 = 0%) (Figure 1).16,17 From the unadjusted num-
bers in the trials, the pooled control event rate (risk of
influenzalike illness) was 24.7% over 6 weeks. Applying
the cluster-adjusted RR, mask use would reduce this to
20.5%, a 4.2% absolute risk reduction or an NNT of 24.
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Table 2. Study characteristics of mask use in health care workers to prevent viral respiratory tract infections
RCT (CLUSTER:
YES OR NO) COUNTRY,
SETTING POPULATION
(AGE)
SAMPLE SIZE
ENROLLED
(ANALYZED)
CLUSTERS
(RANDOM-
IZED) INTERVENTIONS
WHO
WORE
THE
MASKS MASK USE
RECOMMENDATION ADHERENCE
Jacobs et al,
 (no) Japan,
tertiary
care
hospital
Health care
workers
(mean
.y)
 () NA Mask (), no
mask () Health
care
workers
(not sick)
Health care
workers wear
masks while on
hospital
property and
performing
their roles
. of
participants self-
reported “full
compliance,
with the
remaining
complying 
to  of the
time (applies to
both mask use
and nonuse)
Loeb et al,
 (no) Canada,
tertiary
hospitals
Nurses
(mean y)  () NA Surgical masks
(), N
masks ()
Nurses When caring for
patients with
febrile
respiratory
illness
All  participants
allocated to
surgical masks
wore them when
caring for patients
admitted to unit
in droplet
precautions for
influenza
MacIntyre et
al, 
(yes)
China,
hospital
(ED and
respiratory
wards)
Nurses,
doctors,
ward clerks
(mean  y)
 () Cluster: unit
of random-
ization was
hospital (
hospitals
involved, 
per study
arm)
Surgical masks
(), N fit-
tested masks
(), N
masks not fit-
tested ()
Health
care
workers
Every shift
(given 
surgical masks
daily or  N
masks daily)
Worn   on
working days:
surgical, 
(h/day); N fit,
 (. h/day);
N no fit, 
(. h/day)
MacIntyre et
al, 
(yes)
China,
hospitals
(ED and
respiratory
wards)
Nurses,
doctors
(mean
.y)
Surgical
mask  
(),
targeted use
of N  
(),
N  
(),
total  
()
 wards at
 sites Surgical masks
(), targeted
use of N
masks (),
N masks ()
Nurses,
doctors All the time
(surgical
masks), as
needed
(targeted N
masks), all the
time (N
masks)
 for surgical
masks,  for
N targeted
masks,  for
N masks
MacIntyre et
al, 
(yes)
Vietnam,
hospitals
(ED, ICU, ID
or
respiratory
wards,
pediatric
ward)
Nurse or
doctor
(mean  y)
 ()  wards at
 sites Surgical masks
(), cloth
masks (-layer
cotton) (),
control ()—
“standard
practice” of
mask use
Nurses
or
doctors
Surgical masks:
all the time on
shift; cloth
masks: all the
time on shift;
control:
standard
practice
Surgical masks
., cloth
masks .,
standard
practice .
Radonovich
et al, 
(yes)
US,
outpatient
sites
(clinics,
primary
care clinics,
EDs)
Health care
personnel
(mean  y)
 health
care
personnel
seasons 

participants
(
seasons)
 clusters
at  sites Surgical masks
( person-
seasons), N
masks (
person-
seasons)—note
that  person
could be in
different arms
each of the 
seasons
Those
involved
in direct
patient
care
Whenever
positioned
within  ft of a
patient with
suspected or
confirmed
respiratory
illness
N: .
always, .
sometimes;
surgical: .
always, .
sometimes
ED—emergency department, ICU—intensive care unit, ID—infectious disease, NA—not applicable, RCT—randomized controlled trial, US—United States.
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Note that the definition of influenzalike illness in these tri-
als was broad: cough and at least 1 constitutional symp-
tom such as chills or fever.
Health care setting
Of the 6 RCTs examining the use of masks by health
care workers, only 2 had a control group assigned to
“no mask.”28,32 In these trials, masks did not reduce influ-
enzalike illness (RR = 0.26; 95% CI 0.01 to 6.42; 1 trial),
any clinical respiratory infection (RR = 0.74; 95% CI 0.36
to 1.54; I2 = 0%), confirmed influenza (RR = not estimable),
or confirmed viral respiratory infection (RR = 0.90; 95% CI
0.33 to 2.44; 1 trial), compared with no masks. However,
1 of the 2 trials was small (32 participants) and the over-
all number of events were low (only 62 cases of clini-
cal respiratory infections in a total of 1160 individuals),
leading to imprecision (see analysis 2 in Appendix 2
for forest plots*). Also, in the larger trial (n = 1038 for
the “masks” vs “no mask” comparison), there was a
high contamination rate, with 99% of the participants
assigned to the control group reporting use of some
kind of mask at some point.32
In the only trial comparing surgical masks to cloth
masks, results favoured surgical masks over cloth masks
for reduction in clinical or laboratory-confirmed viral
respiratory infections; however, results were not sta-
tistically significant (see analysis 3 in Appendix 2 for
forest plots*).32 Influenzalike illness risk was signifi-
cantly reduced with surgical masks compared with cloth
masks (RR = 0.12; 95% CI 0.02 to 0.98) but again event
rates were low, explaining the large CI and limiting the
certainty of this result. The event rate in the cloth mask
group (risk of influenzalike illness) was 2.3% over 4
weeks. Applying the cluster-adjusted RR, surgical mask
use would reduce this risk to 0.3%, a 2% absolute risk
reduction or an NNT of 50.
Four RCTs compared the use of surgical and N95
masks in health care workers.29-31,33 In these trials, we
Table 3. Outcomes for mask use to prevent viral respiratory tract infections
MASK USERS
CONFIRMED INFLUENZA CONFIRMED VIRAL
RESPIRATORY INFECTION INFLUENZALIKE ILLNESS ANY RESPIRATORY INFECTION
RCTS (N*) RR (95% CI) RCTS (N*) RR (95% CI) RCTS (N*) RR (95% CI) RCTS (N*) RR (95% CI)
Community
• Community
members  () .
(.-.)  () NA  () .
(.-.)  () NA
• Families—sick
wearing masks  () NA  () .
(.-.)  () .
(.-.)  () .
(.-.)
• Families—
healthy
wearing masks
() .
(.-.) () .
(.-.) () .
(.-.)  () NA
• Families—
healthy and
sick wearing
masks
 () .
(.-.)  () NA  () .
(.-.)  () NA
• Communities
staying in
tents
 () .
(.-.)  () .
(.-.)  () .
(.-.)  () .
(.-.)
• Families—given
masks before
illness
 () NA  () NA  () .
(.-.)  () NA
Health care
workers
• Masks vs
nothing  () Not
estimable  () .
(.-.)  () .
(.-.)  () .
(.-.)
• N masks vs
surgical masks () .
(.-.) () .
(.-.) () .
(.-.) () .
(.-.)
• Surgical masks
vs cloth masks  () .
(.-.)  () .
(.-.)  () .
(.-.)  () .
(.-.)
NA—not applicable, RCT—randomized controlled trial, RR—risk ratio.
*The number of patients is modified (reduced) to account for clustering.
Results calculated using a fixed-effects model.
One RCT had  arms.
Two of the included RCTs had  arms, so  RCTs would be  arms and  RCTs would be  arms.
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found no difference between surgical and N95 masks
for confirmed influenza (RR = 1.10; 95% CI 0.91 to 1.32;
I2 = 0%) or confirmed viral respiratory infections (RR = 0.95;
95% CI 0.83 to 1.07; I2 = 0%). N95 masks appeared to
reduce influenzalike illness (RR = 0.78; 95% CI 0.61
to 1.00; I2 = 0%) and any clinical respiratory infection risk
(RR = 0.95; 95% CI 0.90 to 1.00; I2 = 55%) (Figure 2, avail-
able from CFPlus*). The pooled control event rate for
influenzalike illness from the unadjusted numbers in the
trials was 4.6% over 4 to 12 weeks (1 study looking at
12 weeks each year for 4 years for a total of 48 weeks,
but using individual seasons as their unit of analysis) of
wearing surgical masks. Applying the cluster-adjusted
RR, N95 masks would reduce this risk to 3.6%, a 1%
absolute risk reduction or an NNT of 100. The pooled
control event rate for clinical respiratory infections from
the unadjusted numbers in the trials was 49.4% over 4
to 12 weeks of wearing surgical masks. Applying the
cluster-adjusted RR, N95 masks would reduce this risk
to 46.9%, meaning a 2.5% absolute risk reduction or an
NNT of 40. To account for differences in trials compar-
ing N95 masks with surgical masks, the random-effects
model demonstrated a more conservative estimate with
wider CIs, reducing the certainty of a positive effect
for both influenzalike illness (RR = 0.79, 95% CI 0.62 to
1.02; I2 = 0%) and for any clinical respiratory infections
(RR = 0.69, 95% CI 0.47 to 1.03; I2 = 55%) (see analyses 4
and 5 in Appendix 2 for full details*).
Discussion ——
Overall, we found limited evidence regarding the effect of
masks on viral respiratory infections both in the commu-
nity and in health care settings, and most of our analyses
showed no statistically significant differences. Particularly
in the community setting, we wanted to see if there was
any evidence of benefit from systematic use of masks
by the general public outside the home, but we found
no such evidence. Our review still identified 4 poten-
tially important results. First, the use of masks by a group
in the community setting appears to reduce influenza-
like illness in those wearing masks. While community
trials that most closely aligned with mask use in real-
life community settings16,17 did not show significant
effects individually, our pooled analysis showed a signifi-
cant risk reduction (NNT = 24). Although the same analy-
sis showed no significant risk reduction in confirmed
influenza or confirmed viral infection, we believe influ-
enzalike illness to be an important patient-oriented out-
come. Second, using masks within a family 1 to 3 days
after someone has developed symptoms of a viral respi-
ratory infection does not appear to prevent transmission
to family members, no matter if the masks are used by
the sick individual, the healthy family members, or both.
Third, surgical masks are likely superior to cloth masks
for preventing influenzalike illness in health care workers
(NNT = 50) but our results are drawn from a single study.32
Finally, N95 masks are likely superior to surgical masks
for preventing influenzalike illness (NNT = 100) and clinical
respiratory infections (NNT = 40) in health care workers.
There are many potential reasons why RCTs of masks
have historically struggled to find statistically significant
differences. The first reason might simply be that masks
do not prevent viral respiratory infection transmission.
Some have postulated this is because people are not
using them properly, are touching their face while wear-
ing one, or are wearing it below their nose. Some also
postulated that people using masks might feel protected
and might be less likely to follow other recommenda-
tions such as hand hygiene. A host of other reasons are
also mentioned; however, these reasons remain hypoth-
eses and are unproven. Second, many studies use a
cluster-randomized design, which reduces the power of
these studies and the ability to achieve statistical sig-
nificance if indeed there is a difference. Third, adher-
ence to wearing masks is generally poor. For example,
most community studies found that mask use averaged
5 hours or less per day or that 50% of participants or less
reported regular use. And even if the rate of adherence
was high, most studies had particular instructions about
when to wear masks. For example, all studies in health
care workers instructed participants in the mask group
to wear a mask when at work. These individuals could
therefore get infected outside work, while not wearing
Figure 1. Daily mask use compared with no mask use in the community to prevent influenzalike illness
STUDY OR SUBGROUP
MASKS CONTROL
WEIGHT, % RISK RATIO* (95% CI) RISK RATIO* (95% CI)EVENTS TOTAL EVENTS TOTAL
Aiello, 2010 99 378 177 552 73.7 0.82 (0.66-1.01)
Aiello, 2012 45 387 50 366 26.3 0.85 (0.58-1.24)
Total (95% CI) 765 918 100.0 0.83 (0.69-0.99)
Total events 144 227
Heterogeneity: c2
1 = 0.04 (P = .85); I2 = 0% 0.01 0.1 1 10 100
Test for overall effect: Z = 2.05 (P = .04) Favours masks Favours control
*Mantel-Haenszel fixed-effects method.
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a mask, influencing the overall results. In other studies,
mask use in the control arm also occurred. For example,
in the Alfelali et al study,18 masks were used by 25% of
the individuals in the mask arm and 14% of the individu-
als in the no-mask arm, making any separation of effect
less likely. Fourth, in some studies, event rates (eg, influ-
enza cases) were low, with only a few cases in either
arm, reducing the ability of the studies to determine sta-
tistical significance if there is a difference. This might
explain why we found significant risk reduction in more
common outcomes such as influenzalike illness and any
clinical respiratory infection, but not in confirmed influ-
enza or confirmed viral infection. Fifth, many commu-
nity studies were designed to start mask use after the
index patient was seen by a health care provider. This
means patients might have already been sick at home
for 1 to 3 days, potentially transmitting infection to fam-
ily members and making mask introduction potentially
useless. Sixth, in health care workers, the comparison of
N95 and surgical masks might not reach clear statistical
significance simply because both interventions might be
beneficial and differences between the 2 might be small.
It might also be because in all but 1 study, N95 masks
and surgical masks were used either all the time at work
or when caring for patients with respiratory illness, not
only in particularly high-risk situations (eg, intubation)
where N95 masks might be more warranted.
Strengths and limitations
This review has some limitations and notable remaining
uncertainties. Our search strategy pertaining to articles
published before January 1, 2020, was limited to sys-
tematic reviews and might have kept us from finding
additional RCTs. Our review did not identify any study
examining if wearing masks in a large community such
as a city prevents the spread of infection to others. The
studies of sick individuals wearing masks to prevent
secondary infection of family members did not find ben-
efit but had many limitations as mentioned above; there-
fore, we do not yet know if wearing masks will reduce
transmission to others. Our review did not find any RCTs
investigating the use of cloth masks in the community.
Pertaining to the use of masks by health care work-
ers, we found no studies conducted in primary care and
almost no evidence comparing wearing a mask to not
wearing a mask. The last is not surprising, as having
a “no mask” group raises ethical issues. Regarding our
analysis, the most correct way to perform these meta-
analyses is debatable. We chose to pool event rates
adjusted only for clustering rather than pooling adjusted
effect estimates (eg, odds ratios). We did this to mini-
mize other adjustments and to avoid selecting results
with different levels of adjustment, thereby maintain-
ing consistency in our analysis. Also, we tried to pool
studies into similar clinical scenarios and believed fixed-
effects models for analysis were the most appropriate.
We did, however, perform random-effects sensitivity
analyses when some design heterogeneity remained (as
in the comparison of N95 and surgical masks in health
care workers). We looked at multiple outcomes and did
numerous analyses, therefore increasing the probabil-
ity that our positive results are owing to chance. Our
review focused on masks and did not account for the
benefits of other preventive interventions such as hand
hygiene or additional PPE.
Our review also had a number of strengths includ-
ing using only RCTs, adjustment for cluster design, and
pooling based on clinical similarities.
None of the studies in this review included patients
with COVID-19. Future research on masks for the pre-
vention of COVID-19 in health care and community set-
tings is very much needed. In addition, the effect of cloth
masks on community prevention of any viral respira-
tory illness should be studied, as no RCTs exist to assess
their benefit.
Conclusion
Our systematic review found limited evidence that the
use of masks might reduce the risk of viral respiratory
infections. In the community setting, we found no evi-
dence regarding the use of masks by the general public
outside the home, but found a possible reduction on the
risk of influenzalike illness when masks are used at least
a few hours a day by a population in a specific area. In
health care workers, the best available evidence shows
no difference between N95 masks and surgical masks
on the risk of confirmed influenza or other confirmed
viral respiratory infections, although our results suggest
a possible benefit from N95 masks for preventing influ-
enzalike illness or other clinical respiratory infections.
Surgical masks might be superior to cloth masks but
data are limited to 1 trial.
Dr Dugré is a pharmacist at the CIUSSS du Nord-de-l’Ile-de-Montréal in Quebec and
Clinical Assistant Professor in the Faculty of Pharmacy at the University of Montreal.
Dr Ton is a pharmacist and Clinical Evidence Expert at the College of Family Physicians
of Canada in Edmonton. Ms Perry is Knowledge Translation Expert at the Alberta
College of Family Physicians in Edmonton. Dr Garrison is Associate Professor in the
Department of Family Medicine at the University of Alberta in Edmonton. Dr Falk
is Associate Professor in the College of Pharmacy at the University of Manitoba in
Winnipeg. Dr McCormack is Professor in the Faculty of Pharmaceutical Sciences at
the University of British Columbia in Vancouver. Dr Moe is Clinical Evidence Expert
at the College of Family Physicians of Canada in Mississauga, Ont. Dr Korownyk is
Associate Professor in the Department of Family Medicine at the University of Alberta.
Dr Lindblad is Knowledge Translation and Evidence Coordinator at the Alberta College
of Family Physicians and Associate Clinical Professor in the Department of Family
Medicine at the University of Alberta. Dr Kolber is Professor in the Department of
Family Medicine at the University of Alberta. Ms Thomas is Knowledge Translation
Expert at the Alberta College of Family Physicians. Dr Train is Assistant Professor in
the Department of Family Medicine at Queen’s University in Kingston, Ont. Dr Allan
is Director of Programs and Practice Support at the College of Family Physicians of
Canada and Professor in the Department of Family Medicine at the University of Alberta.
Acknowledgment
We thank our peer reviewers for their valuable feedback.
Contributors
All authors were part of the Evidence Review Team and contributed to preparing the
manuscript for submission.
Competing interests
None declared
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Correspondence
Dr Nicolas Dugré; e-mail nicolas.dugre@umontreal.ca
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This article has been peer reviewed.
Cet article a fait l’objet d’une révision par des pairs.
Can Fam Physician ;:-
... Let us scrutinize your hypocrisy, by way of contrast . . . 15 In stark contrast, in the current scenario, you have open hostility against low-cost treatments for COVID-19. You took the opposite tact; you derided the medical doctors involved; essentially condemned hydroxychloroquine treatments against SARS-CoV-2. ...
... With this as context, the Director of NIAID, Dr. Anthony S. Fauci, embraces the following? 15 Please see section above, "Censorship-of and Outright Threats Against Those Associated with Hydroxychloroquine," Pages 4 -8. 16 Please see footnote 15. ...
... 15 Please see section above, "Censorship-of and Outright Threats Against Those Associated with Hydroxychloroquine," Pages 4 -8. 16 Please see footnote 15. Please see Question 3, Page 9 above. ...
... Let us scrutinize your hypocrisy, by way of contrast . . . 15 In stark contrast, in the current scenario, you have open hostility against low-cost treatments for COVID-19. You took the opposite tact; you derided the medical doctors involved; essentially condemned hydroxychloroquine treatments against SARS-CoV-2. ...
... With this as context, the Director of NIAID, Dr. Anthony S. Fauci, embraces the following? 15 Please see section above, "Censorship-of and Outright Threats Against Those Associated with Hydroxychloroquine," Pages 4 -8. 16 Please see footnote 15. ...
... 15 Please see section above, "Censorship-of and Outright Threats Against Those Associated with Hydroxychloroquine," Pages 4 -8. 16 Please see footnote 15. Please see Question 3, Page 9 above. ...
Technical Report
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Alleged "COVID-19 Pandemic" mandated government enforced lockdowns of citizens, leading to massive but ignored K -12 suicide deaths of our children is connectable to Dr. Anthony Fauci.
... 31 There is limited evidence that the use of masks might reduce the risk of viral respiratory infections. 32 According to MacIntyre et al, 33 there was a higher risk of coronavirus infection in health care workers who wore a mask compared to a respirator. No evidence exists to claim the face masks during exercise offer additional protection from the droplet transfer of the virus. ...
Article
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This commentary discusses if targeted uses of face masks may provide better results than generalized face masks mandates to limit the spread of Covid-19. The study is based on a literature review, as well as the analysis of cases and fatalities of different countries adopting different mask mandates. Before the Covid-19 emergency, the literature was consistently against generalized masking for cold and flu viruses. The latest literature for Covid-19 infection is opposite mostly supportive for generalized masking, even if contrarian works exist. The Covid-19 recommendations are not based on randomized controlled trials of healthy individuals wearing or not masks, differentiating in between closed or open spaces. Countries that did not mandate face masks have not performed worse for the number of cases and fatalities than countries that adopted generalized face masking policies during the Covid-19 emergency. Face masks help against Covid-19 infection but also have downfalls. Their benefits are overestimated, while their risks are underestimated. Masks can block the larger droplets exhaled by an infected wearer, protecting the healthy from viral exposure, but their ability to filter out viruses is variable and generally poor especially in reused cloth masks worn by the public. New surgical masks should be used in crowded spaces especially indoors, preferring distancing without masks outdoor. There are serious unintended consequences from wearing face masks improperly and for too long that must be accounted for. There could be more advantages from targeted rather than generalized uses of only surgical face masks.
... Many previous studies have reported the importance of using a mask to prevent infection. A study by Dugré et al. 10 found that the use of masks by health-care workers and the general public reduced the risk of respiratory viral infections. And also, according to a study by Leung et al., 11 the use of masks in public places and public facilities was found to be effective in preventing COVID-19 infection. ...
Article
Objective: As of July 25, 2021, the Korea Disease Control and Prevention Agency reported 1,422 new coronavirus disease 2019 (COVID-19) cases, 188,848 total cases, and 2,073 total deaths (1.10% fatality rates). Since the first severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) case was reported, efforts to find a treatment and vaccine against COVID-19 have been widespread. Methods: Four vaccines are on the World Health Organization's (WHO's) emergency use listing and are approved of their usage; BNT162b2, mRNA-1273, AZD1222, and Ad26.COV2.S. Vaccines against SARS-CoV-2 need at least 14 d to achieve effectiveness. Thus, people should abide by prevention and control measures, including wearing masks, washing hands, and social distancing. Results: However, a lot of new cases were reported after vaccinations, as many people did not follow the prevention control measures before the end of the 14-d period. There is no doubt we need to break free from mask mandates. Conclusions: But let us not decide the timing in haste. Even if the mask mandates are eased, they should be changed depending on the number of reported cases, vaccinations, as well as prevention and control measures on how circumstances are changing under the influence of mutant coronavirus.
... Clearly, surgical masks protect the wearer less than they protect others: they produce less outward transmission. This is in essence what IHME and WHO also affirm, as do other recent studies (Marasinghe, 2020;Dugré et al, 2020). Greenhalgh et al. defend that policy makers should apply the "precautionary principle" and encourage people to wear face masks on the grounds that "we have little to lose and potentially something to gain from this measure" . ...
Article
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Objective. Widely present pandemic-related stress resulting from the use of face masks needs definition, evaluation and treatment. Mouth coverings hamper communication, increasing stress that possibly compromises the immune system and psychological well-being of patients, health professionals and general population. Most present mouth coverings have limited antiviral efficacy but possess social and political value in addition to positive and negative psychological implications. Transparent filtering materials have become available and may help reduce communication stress, alongside several cognitive approaches. Method. A systematic search was performed of the period 2000-2020 using the keywords, with no language limits, of databases including MEDLINE/PubMed, Science Direct, PsycInfo, Google Scholar and Cochrane. The search produced 247 articles, of which 84 were partly relevant. Conclusion. Communication stress showed to be relevant in all clinical situations and in the general population. Currently no specific solutions for face mask-related communication stress are available, save for an increased use of body language and stress management. Transparent face coverings could be a panacea. Treatment of pandemic-related stress should have specific itemized protocols.
... In this issue of Eurosurveillance, Brainard et al. reviewed 12 randomised trials and 21 observational studies of the effectiveness of face mask use against respiratory virus transmission [17]. The meta-analysis of randomised trials has similar findings to a number of earlier Cochrane reviews [18][19][20][21] and published systematic reviews and meta-analyses [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], namely that face mask interventions could probably reduce transmission by a small margin but not a large margin in the community. Brainard et al. estimate that masks reduce the risk of infection by around 6% to 15% [17]. ...
... The first, as suggested by epidemiology reports on COVID-19 (Li et al., 2020a), is a contagious asymptomatic patient requiring dental treatments, not yet diagnosed for SARS-CoV-2. Under these conditions, the use of PPE appears critical to reduce the possible risk of infection (Dugré et al., 2020;. The secondary focused question was on the use of surface disinfection and protective masks to protect against airborne pathogens and directly transmitted viral pathogens that cause respiratory infections. ...
Article
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Objectives: Primary focused question for this systematic review (SR) was: "Which is the evidence about surfaces decontamination and protection masks for SARS-Cov-2 in dental practice?". Secondary question was: "Which is the evidence about surfaces decontamination and protection masks against airborne pathogens and directly transmitted viral pathogens causing respiratory infections?" Materials and methods: PRISMA guidelines were used. Studies on surfaces decontamination and protective masks for SARS-Cov-2 in dental practice were considered. Studies on other respiratory viruses were considered for the secondary question. Results: No studies are available for SARS-Cov-2. Four studies on surfaces disinfection against respiratory viruses were included. Ethanol 70% and sodium hypochlorite 0,5% seems to be effective in reducing infectivity by >3log TCID. Four RCTs compared different types of masks on HCW. The single studies reported no difference for laboratory-diagnosed influenza, laboratory-diagnosed respiratory infection and influenza like illness. A meta-analysis was not considered appropriate. Conclusions: There is lack of evidence on the efficacy of surfaces disinfection and protective masks to reduce the spread of SARS-CoV-2 or other respiratory viruses in dentistry. However, the consistent use of respirator and routine surfaces disinfection is strongly suggested. There is urgent need of data on the efficacy of specific protection protocols for dental HCW against viral infections.
... We identified several major knowledge gaps requiring further research, most fundamentally an improved characterization of the modes of person-toperson transmission. Canadian Family Physician, July 2020): [15] (p. 509, Abstract) Synthesis In total, 11 systematic reviews were included and 18 RCTs of 26 444 participants were found, 12 in the community and 6 in health care workers. ...
Technical Report
A vile new mantra is on the lips of every public health official and politician in the global campaign to force universal masking on the general public: “there is a growing body of evidence”. This propagandistic phrase is a vector designed to achieve five main goals: - Give the false impression that a balance of evidence now proves that masks reduce the transmission of COVID-19 - Falsely assimilate commentary made in scientific venues with “evidence” - Hide the fact that a decade’s worth of policy-grade evidence proves the opposite: that masks are ineffective with viral respiratory diseases - Hide the fact that there is now direct observational proof that cloth masks do not prevent exhalation of clouds of suspended aerosol particles; above, below and through the masks - Deter attention away from the considerable known harms and risks due to face masks, applied to entire populations The said harms and risks include that a cloth mask becomes a culture medium for a large variety of bacterial pathogens, and a collector of viral pathogens; given the hot and humid environment and the constant source, where home fabrics are hydrophilic whereas medical masks are hydrophobic. In short, I argue: op-eds are not “evidence”, irrelevance does not help, and more bias does not remove bias. Their mantra of “a growing body of evidence” is a self-serving contrivance that impedes good science and threatens public safety. I prove that there is no policy-grade evidence to support forced masking on the general population, and that all the latest-decade’s policy-grade evidence points to the opposite: NOT recommending forced masking of the general population. Therefore, the politicians and health authorities are acting without legitimacy and recklessly.
... A very recent systematic review by Macintyre and Chughtai 7 of public masking studies (including many RCTs) concluded that masks are effective at slowing the spread of many respiratory diseases. Additional RCTs on this subject are coming out frequently 55 . However, there are not, to our knowledge, any COVID-19 specific RCTs yet published. ...
Technical Report
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Scientific evidence can be difficult to interpret under the best of circumstances. During a global pandemic (and election year), it is no surprise that there is public confusion about what measures can effectively protect families and communities from COVID-19. Because the scientific and medical understanding of this disease is advancing so rapidly, we decided to put together a plain-language summary of the science on face coverings—a.k.a. masks. As lifelong residents of Utah County and scientists, we felt a responsibility to respond to the technical questions asked by friends and family. We did not receive any funding to carry out this work, nor do we plan on seeking financial support on this topic (our BYU lab mainly researches water and air pollution: benabbott.byu.edu). Our four-person team compiled and read over 115 scientific studies on COVID-19. These studies were done by independent groups from all around the U.S. and the world. In the paragraphs below, we have done our best to accurately reflect the scientific evidence, pointing out where it is solid and where there is still uncertainty. There are three sections, with increasing levels of detail: 1. An executive summary, 2. A list of common questions, and 3. A deep dive. We hope this summary is useful to you as you decide what is best for your family and as our community decides how best to face this threat together.
Article
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Purpose: This study analyzed the current status of face mask usage. It also identified factors related to the knowledge and behavior regarding the same among older adults living alone during the COVID-19 pandemic. Methods: This descriptive study was conducted via a telephone survey involving 283 older adults living alone in S City from March to April 2020. Knowledge and behavior pertaining to face mask usage were measured using Hilda Ho's Face Mask Use Scale; reliability of the measurement was Kuder-Richardson formula-20 = .62, Cronbach's α = .92. Data were analyzed using descriptive analysis, independent t-test, Pearson's correlation coefficient, and multiple linear regression. Results: Older adults used one mask for 3.55 days on an average. The knowledge level was 9.97 (± 1.84) out of 12 and behavior level was 15.49 (± 1.55) out of 16. Level of education (β = - .31, p < .001), living region (β = .13, p = .017), personal income (β = .12, p = .041) significantly affected the face mask usage-related knowledge, and living region (β = .15, p = .010) significantly affected the face mask usage-related behavior. Conclusion: Older adults living alone are aware of the effects of using face masks. However, their mask usage is inappropriate, for example, the prolonged use of the same mask. Considering the low level of face mask usage-related knowledge, it is necessary to develop customized education programs and infectious disease prevention strategies for older adults possessing low educational levels living alone in urban-rural complex areas.
Article
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There were 3 influenza pandemics in the 20th century, and there has been 1 so far in the 21st century. Local, national, and international health authorities regularly update their plans for mitigating the next influenza pandemic in light of the latest available evidence on the effectiveness of various control measures in reducing transmission. Here, we review the evidence base on the effectiveness of nonpharmaceutical personal protective measures and environmental hygiene measures in nonhealthcare settings and discuss their potential inclusion in pandemic plans. Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza. We similarly found limited evidence on the effectiveness of improved hygiene and environmental cleaning. We identified several major knowledge gaps requiring further research, most fundamentally an improved characterization of the modes of person-to-person transmission.
Article
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Background Respiratory protective devices are critical in protecting against infection in health care workers at high risk of novel 2019 coronavirus disease (COVID‐19); however, recommendations are conflicting and epidemiological data on their relative effectiveness against COVID‐19 are limited. Purpose To compare medical masks to N95 respirators in preventing laboratory confirmed viral infection and respiratory illness including coronavirus specifically in health care workers. Data Sources MEDLINE, Embase and CENTRAL from January 1st 2014 to March 9th 2020. Update of published search conducted from January 1st 1990 to December 9th 2014. Study Selection Randomized controlled trials (RCTs) comparing the protective effect of medical masks to N95 respirators in health care workers. Data Extraction Reviewer pair independently screened, extracted data, and assessed risk of bias and the certainty of the evidence. Data Synthesis Four RCTs were meta‐analysed adjusting for clustering. Compared to N95 respirators; the use of medical masks did not increase laboratory confirmed viral (including coronaviruses) respiratory infection (OR 1.06; 95% CI 0.90‐1.25; I²=0%; low certainty in the evidence) or clinical respiratory illness (OR 1.49; 95%CI 0.98‐2.28; I²=78%; very low certainty in the evidence). Only one trial evaluated coronaviruses separately and found no difference between the two groups (p=0.49). Limitations Indirectness and imprecision of available evidence. Conclusions Low certainty evidence suggests that medical masks and N95 respirators offer similar protection against viral respiratory infection including coronavirus in health care workers during non‐aerosol generating care. Preservation of N95 respirators for high‐risk, aerosol generating procedures in this pandemic should be considered when in short supply.
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Objective: To determine the effects of medical cannabinoids on pain, spasticity, and nausea and vomiting, and to identify adverse events. Data sources: MEDLINE, the Cochrane Database, and the references of included studies were searched. Study selection: Systematic reviews with 2 or more randomized controlled trials (RCTs) that focused on medical cannabinoids for pain, spasticity, or nausea and vomiting were included. For adverse events, any meta-analysis for the conditions listed or of adverse events of cannabinoids was included. Synthesis: From 1085 articles, 31 relevant systematic reviews were identified including 23 for pain, 5 for spasticity, 6 for nausea and vomiting, and 12 for adverse events. Meta-analysis of 15 RCTs found more patients taking cannabinoids attained at least a 30% pain reduction: risk ratio (RR) of 1.37 (95% CI 1.14 to 1.64), number needed to treat (NNT) of 11. Sensitivity analysis found study size and duration affected findings (subgroup differences,P≤ .03), with larger and longer RCTs finding no benefit. Meta-analysis of 4 RCTs found a positive global impression of change in spasticity (RR = 1.45, 95% CI 1.08 to 1.95, NNT = 7). Other results were not consistently statistically significant, but when positive, a 30% or more improvement in spasticity had an NNT of 10. Meta-analysis of 7 RCTs for control of nausea and vomiting after chemotherapy found an RR of 3.60 (95% CI 2.55 to 5.09) with an NNT of 3. Adverse effects caused more patients to stop treatment (number needed to harm [NNH] of 8 to 22). Individual adverse events were very common, including dizziness (NNH = 5), sedation (NNH = 5), confusion (NNH = 15), and dissociation (NNH = 20). "Feeling high" was reported in 35% to 70% of users. The GRADE (Grading of Recommendations Assessment, Development and Evaluation) evaluation reduced evidence ratings of benefit to low or very low. Conclusion: There is reasonable evidence that cannabinoids improve nausea and vomiting after chemotherapy. They might improve spasticity (primarily in multiple sclerosis). There is some uncertainty about whether cannabinoids improve pain, but if they do, it is neuropathic pain and the benefit is likely small. Adverse effects are very common, meaning benefits would need to be considerable to warrant trials of therapy.
Article
Objective: To determine how many patients with chronic osteoarthritis pain respond to various non-surgical treatments. Data sources: PubMed and the Cochrane Library. Study selection: Published systematic reviews of randomized controlled trials (RCTs) that included meta-analysis of responder outcomes for at least 1 of the following interventions were included: acetaminophen, oral nonsteroidal anti-inflammatory drugs (NSAIDs), topical NSAIDs, serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, cannabinoids, counseling, exercise, platelet-rich plasma, viscosupplementation, glucosamine, chondroitin, intra-articular corticosteroids, rubefacients, or opioids. Synthesis: In total, 235 systematic reviews were included. Owing to limited reporting of responder meta-analyses, a post hoc decision was made to evaluate individual RCTs with responder analysis within the included systematic reviews. New meta-analyses were performed where possible. A total of 155 RCTs were included. Interventions that led to more patients attaining meaningful pain relief compared with control included exercise (risk ratio [RR] of 2.36; 95% CI 1.79 to 3.12), intra-articular corticosteroids (RR = 1.74; 95% CI 1.15 to 2.62), SNRIs (RR = 1.53; 95% CI 1.25 to 1.87), oral NSAIDs (RR = 1.44; 95% CI 1.36 to 1.52), glucosamine (RR = 1.33; 95% CI 1.02 to 1.74), topical NSAIDs (RR = 1.27; 95% CI 1.16 to 1.38), chondroitin (RR = 1.26; 95% CI 1.13 to 1.41), viscosupplementation (RR = 1.22; 95% CI 1.12 to 1.33), and opioids (RR = 1.16; 95% CI 1.02 to 1.32). Preplanned subgroup analysis demonstrated no effect with glucosamine, chondroitin, or viscosupplementation in studies that were only publicly funded. When trials longer than 4 weeks were analyzed, the benefits of opioids were not statistically significant. Conclusion: Interventions that provide meaningful relief for chronic osteoarthritis pain might include exercise, intra-articular corticosteroids, SNRIs, oral and topical NSAIDs, glucosamine, chondroitin, viscosupplementation, and opioids. However, funding of studies and length of treatment are important considerations in interpreting these data.
Article
Objective: Previous meta-analyses concluded that there was insufficient evidence to determine the effect of N95 respirators. We aimed to assess the effectiveness of N95 respirators versus surgical masks for prevention of influenza by collecting randomized controlled trials (RCTs). Methods: We searched PubMed, EMbase and The Cochrane Library from the inception to January 27, 2020 to identify relevant systematic reviews. The RCTs included in systematic reviews were identified. Then we searched the latest published RCTs from the above three databases and searched ClinicalTrials.gov for unpublished RCTs. Two reviewers independently extracted the data and assessed risk of bias. Meta-analyses were conducted to calculate pooled estimates by using RevMan 5.3 software. Results: A total of six RCTs involving 9 171 participants were included. There were no statistically significant differences in preventing laboratory-confirmed influenza (RR = 1.09, 95% CI 0.92-1.28, P > .05), laboratory-confirmed respiratory viral infections (RR = 0.89, 95% CI 0.70-1.11), laboratory-confirmed respiratory infection (RR = 0.74, 95% CI 0.42-1.29) and influenzalike illness (RR = 0.61, 95% CI 0.33-1.14) using N95 respirators and surgical masks. Meta-analysis indicated a protective effect of N95 respirators against laboratory-confirmed bacterial colonization (RR = 0.58, 95% CI 0.43-0.78). Conclusion: The use of N95 respirators compared with surgical masks is not associated with a lower risk of laboratory-confirmed influenza. It suggests that N95 respirators should not be recommended for general public and nonhigh-risk medical staff those are not in close contact with influenza patients or suspected patients.
Article
Importance Clinical studies have been inconclusive about the effectiveness of N95 respirators and medical masks in preventing health care personnel (HCP) from acquiring workplace viral respiratory infections. Objective To compare the effect of N95 respirators vs medical masks for prevention of influenza and other viral respiratory infections among HCP. Design, Setting, and Participants A cluster randomized pragmatic effectiveness study conducted at 137 outpatient study sites at 7 US medical centers between September 2011 and May 2015, with final follow-up in June 2016. Each year for 4 years, during the 12-week period of peak viral respiratory illness, pairs of outpatient sites (clusters) within each center were matched and randomly assigned to the N95 respirator or medical mask groups. Interventions Overall, 1993 participants in 189 clusters were randomly assigned to wear N95 respirators (2512 HCP-seasons of observation) and 2058 in 191 clusters were randomly assigned to wear medical masks (2668 HCP-seasons) when near patients with respiratory illness. Main Outcomes and Measures The primary outcome was the incidence of laboratory-confirmed influenza. Secondary outcomes included incidence of acute respiratory illness, laboratory-detected respiratory infections, laboratory-confirmed respiratory illness, and influenzalike illness. Adherence to interventions was assessed. Results Among 2862 randomized participants (mean [SD] age, 43 [11.5] years; 2369 [82.8%]) women), 2371 completed the study and accounted for 5180 HCP-seasons. There were 207 laboratory-confirmed influenza infection events (8.2% of HCP-seasons) in the N95 respirator group and 193 (7.2% of HCP-seasons) in the medical mask group (difference, 1.0%, [95% CI, −0.5% to 2.5%]; P = .18) (adjusted odds ratio [OR], 1.18 [95% CI, 0.95-1.45]). There were 1556 acute respiratory illness events in the respirator group vs 1711 in the mask group (difference, −21.9 per 1000 HCP-seasons [95% CI, −48.2 to 4.4]; P = .10); 679 laboratory-detected respiratory infections in the respirator group vs 745 in the mask group (difference, −8.9 per 1000 HCP-seasons, [95% CI, −33.3 to 15.4]; P = .47); 371 laboratory-confirmed respiratory illness events in the respirator group vs 417 in the mask group (difference, −8.6 per 1000 HCP-seasons [95% CI, −28.2 to 10.9]; P = .39); and 128 influenzalike illness events in the respirator group vs 166 in the mask group (difference, −11.3 per 1000 HCP-seasons [95% CI, −23.8 to 1.3]; P = .08). In the respirator group, 89.4% of participants reported “always” or “sometimes” wearing their assigned devices vs 90.2% in the mask group. Conclusions and Relevance Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza. Trial Registration ClinicalTrials.gov Identifier: NCT01249625
Article
This systematic review and meta-analysis quantified the protective effect of facemasks and respirators against respiratory infections among healthcare workers. Relevant articles were retrieved from Pubmed, EMBASE, and Web of Science. Meta-analyses were conducted to calculate pooled estimates. Meta-analysis of randomized controlled trials (RCTs) indicated a protective effect of masks and respirators against clinical respiratory illness (CRI) (risk ratio [RR] = 0.59; 95% confidence interval [CI]:0.46-0.77) and influenza-like illness (ILI) (RR = 0.34; 95% CI:0.14-0.82). Compared to masks, N95 respirators conferred superior protection against CRI (RR = 0.47; 95% CI: 0.36-0.62) and laboratory-confirmed bacterial (RR = 0.46; 95% CI: 0.34-0.62), but not viral infections or ILI. Meta-analysis of observational studies provided evidence of a protective effect of masks (OR = 0.13; 95% CI: 0.03-0.62) and respirators (OR = 0.12; 95% CI: 0.06-0.26) against severe acute respiratory syndrome (SARS). This systematic review and meta-analysis supports the use of respiratory protection. However, the existing evidence is sparse and findings are inconsistent within and across studies. Multicentre RCTs with standardized protocols conducted outside epidemic periods would help to clarify the circumstances under which the use of masks or respirators is most warranted. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved.