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A RAPID SYSTEMATIC REVIEW OF THE EFFICACY OF FACE
MASKS AND RESPIRATORS AGAINST CORONAVIRUSES AND
OTHER RESPIRATORY TRANSMISSIBLE VIRUSES FOR THE
COMMUNITY, HEALTHCARE WORKERS AND SICK PATIENTS
C. Raina MacIntyre , Abrar Ahmad Chughtai
PII: S0020-7489(20)30113-9
DOI: https://doi.org/10.1016/j.ijnurstu.2020.103629
Reference: NS 103629
To appear in: International Journal of Nursing Studies
Received date: 24 March 2020
Revised date: 18 April 2020
Accepted date: 21 April 2020
Please cite this article as: C. Raina MacIntyre , Abrar Ahmad Chughtai , A RAPID SYSTEMATIC RE-
VIEW OF THE EFFICACY OF FACE MASKS AND RESPIRATORS AGAINST CORONAVIRUSES
AND OTHER RESPIRATORY TRANSMISSIBLE VIRUSES FOR THE COMMUNITY, HEALTH-
CARE WORKERS AND SICK PATIENTS, International Journal of Nursing Studies (2020), doi:
https://doi.org/10.1016/j.ijnurstu.2020.103629
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1
A RAPID SYSTEMATIC REVIEW OF THE EFFICACY OF FACE MASKS AND RESPIRATORS AGAINST
CORONAVIRUSES AND OTHER RESPIRATORY TRANSMISSIBLE VIRUSES FOR THE COMMUNITY,
HEALTHCARE WORKERS AND SICK PATIENTS.
Authors and affiliations
1. C. Raina MacIntyre, The Kirby Institute, UNSW Medicine, University of New South Wales,
Sydney, Australia (r.macintyre@unsw.edu.au)
2. Abrar Ahmad Chughtai, School of Public Health and Community Medicine, UNSW Medicine,
University of New South Wales, Sydney, Australia (abrar.chughtai@unsw.edu.au)
Correspondence
Abrar Ahmad Chughtai
Lecturer in International Health, Room 228, Level 2 Samuels Building
School of Public Health and Community Medicine, UNSW Medicine,
University of New South Wales, Kensington Campus, Kensington 2052 Australia
Phone: +61 (2) 93851009 (O) +61 470208225 (M) , E mails: abrar.chughtai@unsw.edu.au
Running title:
Efficacy of face masks and respirators against coronavirus disease (COVID-19)
Key words:
Coronavirus, coronavirus disease, COVID19, mask, respirators, personal protective equipment
2
ABSTRACT
Background
The pandemic of COVID-19 is growing, and a shortage of masks and respirators has been reported globally.
Policies of health organizations for healthcare workers are inconsistent, with a change in policy in the US for
universal face mask use. The aim of this study was to review the evidence around the efficacy of masks and
respirators for healthcare workers, sick patients and the general public.
Methods
A systematic review of randomized controlled clinical trials on use of respiratory protection by healthcare
workers, sick patients and community members was conducted. Articles were searched on Medline and
Embase using key search terms.
Results
A total of 19 randomised controlled trials were included in this study – 8 in community settings, 6 in
healthcare settings and 5 as source control. Most of these randomised controlled trials used different
interventions and outcome measures. In the community, masks appeared to be more effective than hand
hygiene alone, and both together are more protective. Randomised controlled trials in health care workers
showed that respirators, if worn continually during a shift, were effective but not if worn intermittently.
Medical masks were not effective, and cloth masks even less effective. When used by sick patients
randomised controlled trials suggested protection of well contacts.
Conclusion
The study suggests that community mask use by well people could be beneficial, particularly for COVID-19,
where transmission may be pre-symptomatic. The studies of masks as source control also suggest a benefit,
and may be important during the COVID-19 pandemic in universal community face mask use as well as in
health care settings. Trials in healthcare workers support the use of respirators continuously during a shift.
3
This may prevent health worker infections and deaths from COVID-19, as aerosolisation in the hospital
setting has been documented.
What is already known about the topic?"
Masks and respirators are commonly used to protect from respiratory infections in three different
indications – for healthcare workers, sick patients and well community members.
Currently there is debate around the use of masks and respirators in healthcare and community
settings.
"What this paper adds
In the community, masks may be more protective for well people.
In healthcare settings continuous use of respirators, is more protective compared to the medical
masks, and medical masks are more protective than cloth masks. Depending on the fabric and
design, some cloth masks may not be safe for healthcare workers.
The use of masks by sick patients is likely protective, and coronaviruses can be emitted in normal
breathing, in fine airborne particles.
4
Background:
The use of personal protective equipment for coronavirus disease (COVID-19) has been controversial, with
differing guidelines issued by different agencies (1). Coronavirus disease is caused by severe acute
respiratory syndrome coronavirus2 (SARS-CoV-2), a beta-coronavirus, similar to severe acute respiratory
syndrome coronavirus2 (SARS CoV) (1). Seasonal alpha and beta coronaviruses cause common colds, croup
and broncholitis. The transmission mode of coronaviruses in humans is similar, thought to be by droplet,
contact and sometimes airborne routes (2-4). The World Health Organization recommends surgical mask for
health workers providing routine care to a coronavirus disease patient (5), whilst the US Centers for Disease
Control and Prevention recommend a respirator (6). Most authorities are recommending that community
members not wear a mask, and that a mask should only be worn by a sick patient (also referred to as source
control) (7). There are more randomised controlled trials of community use of masks in well people than
studies of the use by sick people (source control). The aim of this study was to review the randomised
controlled trials evidence for use of masks and respirators by the community, health care workers and sick
patients for prevention of infection.
Methods: We searched Medline and EmBase for clinical trials on masks and respirators using the key words
“mask”, “respirator”, and “personal protective equipment”. The search was conducted between 1 March to
April 17 2020 and all randomised controlled trials published before the search date were included. Two
authors (CRM and AAC) reviewed the title and abstracts to identify randomised controlled trials on masks
and respirators. We also searched relevant papers from the reference lists of previous clinical trials and
systematic reviews. Studies that were not randomised controlled trials, were about anaesthesia, or not
about prevention of infection were excluded. Animal studies, experimental and observational epidemiologic
studies were also excluded. Studies published in English language were included.
5
We found 602 papers on Medline and 250 on Embase. 820 papers were excluded by title and abstract
review. Full texts were reviewed for 32 papers and 18 were selected in this review. Results were reported
according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria (8).
Results
In general, the results show protection for healthcare workers and community members, and likely benefit
of masks used as source control. We found eight clinical trials (9-16) on the use of masks in the community
(Table 1). In the community, masks appear to be more effective than hand hygiene alone, and both together
are more protective (9, 12). However, the randomised controlled trials which measured both hand hygiene
and masks measured the effect of hand hygiene alone, but not of masks alone (9, 12, 16). Masks were only
examined in combination with hand hygiene. Therefore the protective effect of masks and hand hygiene
combined could be due to both interventions together, or the effect of masks alone. The use of hand
hygiene alone in these trials was not effective. In more than one trial, interventions had to be used within 36
hours of exposure to be effective (9, 15, 16).
To date, six randomised controlled trials (17-22) has been conducted on the use of masks and/or respirators
by healthcare workers in health care settings (Table 2). The healthcare workers trials (Table 2) used different
interventions and different outcome measures, and one was in the outpatient setting. A Japanese study had
only 32 subjects, and likely was underpowered to find any difference between masks and control (18). Two
North American trials of masks and respirators against influenza infection found no difference between the
arms, but neither had a control arm to differentiate equal efficacy from equal inefficacy (17, 22). Without a
control group to determine rates of influenza in unprotected healthcare workers, neither study is able to
determine efficacy if no difference was observed between the two interventions. A serologic study showed
that up to 23% of unprotected healthcare workers (a rate identical to that observed in Loeb the trial, which
also used serology) contract influenza during outbreaks (23), which suggests lack of efficacy. Studies of
6
nosocomial influenza generally find lower influenza attack rates in unprotected healthcare workers than
observed in the Loeb trial (24).
Further problems with this study are that the majority of subjects were defined as having influenza on the
basis of serological positivity (22). The 10% seroconversion to pandemic H1N109 (with no pandemic virus
isolation or positive PCR) observed in the trial, suggests that pandemic H1N109 was circulating in Ontario
before April 2009, which is unlikely. The overall flu rate was 38%, higher than the expected attack rate in a
pandemic (22). The majority of subjects defined as having influenza were by serology.
A serological definition of influenza can be affected by vaccination. The authors claim they excluded
influenza vaccinated subjects in the outcome, but according to Figure 1, these subjects (130 in total) are
included in the analysis. If they had been excluded and even if no other subjects were excluded, the total
analysed would be 348, which is lower than the 422 subjects analysed (22). These 130 vaccinated subjects
should have been excluded entirely from the analysis. The vaccination status of subjects with seropositivity
is not provided in the paper, but it appears people with positive serology due to vaccination may have
wrongly been counted as influenza cases (22).
In both the North American trials, the intervention comprised wearing the mask or respirator when in
contact with recognized ILI or when doing a high risk procedure, which is a targeted strategy (17, 22). One
was in an outpatient setting.(17) We conducted a randomised controlled trial comparing the targeted
strategy tested in the two North American studies, with the wearing of respiratory protection during an
entire shift, and showed efficacy for continual (but not targeted) use of a respirator (19). The study also did
not show efficacy for a surgical mask worn continually, and therefore no difference between a surgical mask
and targeted use of a respirator (19), which is consistent with the findings of the North American trials (17,
7
22). In summary, the evidence is consistent that a respirator must be worn throughout the shift to be
protective. Targeted use of respirators only when doing high risk procedures and medical mask use is not
protective. Another randomised controlled trial we conducted in China showed efficacy for continual use of
a respirator, but not for a mask, and also found fit-testing of the respirator did not affect efficacy (20).
However, this may be specific to the quality of the tested product, and is not generalisable to other
respirators – fit testing is a necessary part of respirator use (25).
For healthcare workers, there is evidence of efficacy of respirators if worn continually during a shift, but no
evidence of efficacy of a mask (19, 20). For hospitals where COVID-19 patients are being treated, there is
growing evidence of widespread contamination of the ward environment, well beyond 2 meters from the
patient, as well as aerosol transmission (2, 26, 27). Several studies have found SARS-CoV-2 on air vents and
in air samples in intensive care units and COVID-19 wards (26, 28, 29), and an experimental study showed
the virus in air samples three hours after aerosolization (30). The weight of this evidence and the
precautionary principle(31, 32), favors respirators for healthcare workers. We showed lower rates of
infection outcomes in the medical mask arm compared to control, but the difference was not significant
(20). It could be that larger trials are needed to demonstrate efficacy of a mask, but any protection is far less
than from a respirator. A trial we conducted in Vietnam of 2-layered cotton cloth masks compared to
medical masks showed a lower rate of infection in the medical mask group, and a 13 times higher risk of
infection in the cloth mask arm (21). The study suggests cloth masks may increase the risk of infection (21),
but may not be generalizable to all home-made masks. The material, design and adequacy of washing of
cloth masks may have been a factor (33). There are no other randomised controlled trial of cloth masks
published, but if any protection is offered by these it would be less than even a medical mask.
8
Table 3 shows the trials of source control. There were five randomised controlled trials identified of masks
used by sick patients (34-37). One was an experimental study of 9 influenza patients, which did not measure
clinical endpoints (34). Participants with confirmed influenza coughed onto a petri dish wearing a N95
respirator or a mask. No influenza grew on the medium. A trial of 105 sick patients wearing a mask (or no
mask) in the household found no significant difference between arms (36). However, the trial was
terminated prematurely and did not meet recruitment targets, so was probably underpowered. One
randomised controlled trial was conducted among Hajj pilgrims, with both well and sick pilgrims wearing
masks, and low rates of ILI were reported among contact of mask pilgrims (37). Our randomised controlled
trial is the largest available, and studied 245 patients randomised to mask or control (35). Compliance was
suboptimal in the mask group and some controls wore masks. The intention to treat analysis showed no
difference, but when analysed by actual mask use, the rate of infection in household contacts was lower in
those who wore masks (35). A trial with an experimental design was published in April 2020, examining a
range of viruses including seasonal human coronaviruses (38). This showed that coronaviruses are
preferentially found in aerosolized particles compared to large droplets, and could be expelled by normal
tidal breathing. Wearing a surgical mask prevented virus from being exhaled.
Discussion
There are more randomised controlled trials of community use of masks in well people (9-16) than studies of
the use by sick people (also referred to as “source control”), and these trials are larger than the few on
source control (34-36). The evidence suggests protection of masks in high transmission settings such as
household and college settings, especially if used early, if combined with hand hygiene and if wearers are
compliant (9, 12-16). If masks protect in high transmission settings, they should also protect in crowded
public spaces, including workplaces, buses, trains, planes and other closed settings. The trial which did not
9
show efficacy used influenza as the outcome measure (10), which is a rare outcome, so requires a larger
sample size for adequate power and may have been underpowered.
For healthcare workers, the only trials to show a difference between respirators and masks demonstrated
efficacy for continuous use of a respirator through a clinical shift, but not masks (19, 20). The two trials
which showed no difference are widely cited as evidence that masks provide equal protection as respirators
(17, 22). However, without a control arm, the absence of difference between arms could reflect equal
efficacy or inefficacy, and it is not possible to draw any conclusions about efficacy. The high rates of
influenza in the Loeb trial suggest equal inefficacy, and further, there were likely misclassified outcomes in
the trial by inclusion of seropositive, vaccinated healthcare workers, which would have biased the results
(22). The outpatient setting in the US trial may have had lower exposure risk than the inpatient setting of
other trials.(17) In both the North American trials, the intervention comprised wearing the mask or
respirator when in contact with recognized ILI or when doing a high risk procedure (17, 22). The underlying
assumption that the majority of infections in healthcare workers occur during self-identified high-risk
exposures is not supported by any evidence. It assumes healthcare workers can accurately identify when
they are risk in a busy, clinical setting, when the majority of infections may occur when healthcare workers
are unaware of the risk (such as when walking through a busy emergency room or ward where aerosolized
virus may be present). Conversely, infections could occur outside the workplace. This could explain the lack
of difference if there was no actual efficacy of either arm and if much of the infection occurs in unrecognised
situations of risk either within or outside the workplace.
In practice, hospital infection control divides infections into droplet or airborne spread, and recommends
droplet (mask) or airborne (respirator) precautions accordingly (39). In a pooled analysis of both healthcare
worker trials, we showed that continual use of a respirator is more efficacious in protecting healthcare
10
workers even against infections assumed to be spread by the droplet route (39). Medical masks did not
significantly protect against viral, bacterial, droplet or other infection outcomes. However, the summary
odds ratio for masks was less than one, which suggests a low level of protection. Targeted use of respirator
protected against bacterial and droplet infections, but not against viral infections, suggesting viral infections
may be more likely to be airborne in the hospital setting (39).
The five available studies of mask use by sick patients suggest a benefit, but are much smaller trials than the
community trials, two without clinical endpoints, and with less certainty around the findings (34-37). Only
3/5 trials examined clinical outcomes in close contacts (35-37).
Many systematic reviews have been conducted on masks, respirators and other PPE in past (40-49). These
reviews generally examined multiple interventions (e.g. masks and hand hygiene etc), often combined
different outcome measures that were not directly comparable and were inconclusive. Moreover, most of
these reviews did not include more recent randomised controlled trials (17, 21). This systematic review only
focuses on masks and respirators and contains all new studies.
In summary, there is a growing body of evidence supporting all three indications for respiratory protection –
community, healthcare workers and sick patients (source control). The largest number of randomised
controlled trials have been done for community use of masks by well people in high-transmission settings
such as household or college settings. There is benefit in the community if used early, and if compliant. They
also found no evidence of efficacy of hand hygiene or health education, suggesting mask use is more
protective than hand hygiene.
11
Respirators protect healthcare workers if worn continually, but not if worn intermittently in self-identified
situations of risk. This supports the suggestion that the health care environment is a risk to healthcare
workers even when not doing aerosol generating procedures or caring for a known infectious patient. For
COVID-19 specifically, the growing body of evidence showing aerosolisation of the virus in the hospital ward
highlights the risk of inadvertent exposure for healthcare workers and supports the use of airborne
precautions at all times on the ward (26, 28, 29). Further, the rule of 1-2 m of spatial separation is not based
on good evidence, with most research showing that droplets can travel further than 2m, and that infections
cannot be neatly separated into droplet and airborne (39, 50). In the UK, one healthcare trust found almost
one in five healthcare workers to be infected with COVID-19 (51). The deaths of healthcare workers from
COVID-19 reflect this risk (52). The use of masks by sick people, despite being the WHO’s only
recommendation for mask use by community members during COVID-19 pandemic, is supported by the
smallest body of evidence. Source control is probably a sensible recommendation given the suggestion of
protection and given specific data on coronaviruses showing protection (38). It may help if visitors and
febrile patients wear a mask in the healthcare setting, whether in primary care or hospitals. Universal face
mask use is likely to have the most impact on epidemic growth in the community, given the high risk of
asymptomatic and pre-symptomatic transmission (53).
Funding
C Raina MacIntyre is supported by a NHMRC Principal Research Fellowship, grant number
1137582.
12
Conflict of intertest
C Raina MacIntyre receives funding from NHMRC (Centre for Research Excellence and Principal
Research Fellowship) and Sanofi currently. She has received funding from 3M more than 5
years ago for face mask research.
Abrar Ahmad Chughtai had testing of filtration of masks by 3M for his PhD more than 5 years
age. 3M products were not used in his research. He also has worked with CleanSpace
Technology on research on fit testing of respirators (no funding was involved).
13
References
1. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y, et al. Epidemiological and clinical
characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive
study. The Lancet. 2020;395(10223):507-13.
2. Ong SWX, Tan YK, Chia PY, Lee TH, Ng OT, Wong MSY, et al. Air, Surface Environmental,
and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome
Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient. JAMA : the journal of the American
Medical Association. 2020.
3. Zhang W, Du R-H, Li B, Zheng X-S, Yang X-L, Hu B, et al. Molecular and serological
investigation of 2019-nCoV infected patients: implication of multiple shedding routes. Emerging
Microbes & Infections. 2020;9(1):386-9.
4. Zou L, Ruan F, Huang M, Liang L, Huang H, Hong Z, et al. SARS-CoV-2 viral load in upper
respiratory specimens of infected patients. New England Journal of Medicine. 2020.
5. World Health Organisation (WHO). Infection prevention and control during health care
when novel coronavirus (nCoV) infection is suspected. Interim guidance 2020 [Available from:
https://www.who.int/publications-detail/infection-prevention-and-control-during-health-care-
when-novel-coronavirus-(ncov)-infection-is-suspected.
6. Center for Disease Control and Prevention (CDC). Interim Healthcare Infection
Prevention and Control Recommendations for Patients Under Investigation for 2019 Novel
Coronavirus. January 2020 2020 [Available from: https://www.cdc.gov/coronavirus/2019-
nCoV/infection-control.html.
7. Chughtai AA, Seale H, Islam MS, Owais M, Macintyre CR. Policies on the use of
respiratory protection for hospital health workers to protect from coronavirus disease (COVID-
19). International journal of nursing studies. 2020;105:103567.
8. Moher D, Shamseer L, Clarke M, Ghersi D, Liberati A, Petticrew M, et al. Preferred
reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement.
Systematic reviews. 2015;4(1):1.
9. Aiello AE, Perez V, Coulborn RM, Davis BM, Uddin M, Monto AS. Facemasks, hand
hygiene, and influenza among young adults: a randomized intervention trial. PloS one.
2012;7(1).
10. Simmerman JM, Suntarattiwong P, Levy J, Jarman RG, Kaewchana S, Gibbons RV, et al.
Findings from a household randomized controlled trial of hand washing and face masks to
reduce influenza transmission in Bangkok, Thailand. Influenza and other respiratory viruses.
2011;5(4):256-67.
11. Larson EL, Ferng Y-H, Wong-McLoughlin J, Wang S, Haber M, Morse SS. Impact of non-
pharmaceutical interventions on URIs and influenza in crowded, urban households. Public
Health Reports. 2010;125(2):178-91.
12. Aiello AE, Murray GF, Perez V, Coulborn RM, Davis BM, Uddin M, et al. Mask use, hand
hygiene, and seasonal influenza-like illness among young adults: a randomized intervention
trial. The Journal of infectious diseases. 2010;201(4):491-8.
13. MacIntyre CR, Cauchemez S, Dwyer DE, Seale H, Cheung P, Browne G, et al. Face mask
use and control of respiratory virus transmission in households. Emerging infectious diseases.
2009;15(2):233.
14
14. Cowling BJ, Fung RO, Cheng CK, Fang VJ, Chan KH, Seto WH, et al. Preliminary findings of
a randomized trial of non-pharmaceutical interventions to prevent influenza transmission in
households. PloS one. 2008;3(5):e2101.
15. Suess T, Remschmidt C, Schink SB, Schweiger B, Nitsche A, Schroeder K, et al. The role of
facemasks and hand hygiene in the prevention of influenza transmission in households: results
from a cluster randomised trial; Berlin, Germany, 2009-2011. BMC infectious diseases.12:26.
16. Cowling BJ, Chan KH, Fang VJ, Cheng CK, Fung RO, Wai W, et al. Facemasks and hand
hygiene to prevent influenza transmission in households: a cluster randomized trial. Annals of
internal medicine.151(7):437-46.
17. Radonovich LJ, Simberkoff MS, Bessesen MT, Brown AC, Cummings DAT, Gaydos CA, et
al. N95 respirators vs medical masks for preventing influenza among health care personnel: A
randomized clinical trial. JAMA - Journal of the American Medical Association. 2019;322(9):824-
33.
18. Jacobs JL, Ohde S, Takahashi O, Tokuda Y, Omata F, Fukui T. Use of surgical face masks
to reduce the incidence of the common cold among health care workers in Japan: a randomized
controlled trial. American journal of infection control. 2009;37(5):417-9.
19. MacIntyre CR, Wang Q, Seale H, Yang P, Shi W, Gao Z, et al. A randomized clinical trial of
three options for N95 respirators and medical masks in health workers. American Journal of
Respiratory & Critical Care Medicine.187(9):960-6.
20. MacIntyre CR, Wang Q, Cauchemez S, Seale H, Dwyer DE, Yang P, et al. A cluster
randomized clinical trial comparing fit-tested and non-fit-tested N95 respirators to medical
masks to prevent respiratory virus infection in health care workers. Influenza & Other
Respiratory Viruses.5(3):170-9.
21. MacIntyre CR, Seale H, Dung TC, Hien NT, Nga PT, Chughtai AA, et al. A cluster
randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ
Open.5(4):e006577.
22. Loeb M, Dafoe N, Mahony J, John M, Sarabia A, Glavin V, et al. Surgical mask vs N95
respirator for preventing influenza among health care workers: a randomized trial. JAMA : the
journal of the American Medical Association.302(17):1865-71.
23. Elder AG, O'Donnell B, McCruden EA, Symington IS, Carman WF. Incidence and recall of
influenza in a cohort of Glasgow healthcare workers during the 1993-4 epidemic: results of
serum testing and questionnaire. BMJ (Clinical research ed). 1996;313(7067):1241-2.
24. Salgado CD, Farr BM, Hall KK, Hayden FG. Influenza in the acute hospital setting. The
Lancet infectious diseases. 2002;2(3):145-55.
25. Chughtai AA, MacIntyre CR, Zheng Y, Wang Q, Toor ZI, Dung TC, et al. Examining the
policies and guidelines around the use of masks and respirators by healthcare workers in China,
Pakistan and Vietnam. J Infect Prev. 2015;16(2):68–74.
26. Santarpia JL, Rivera DN, Herrera V, Morwitzer MJ, Creager H, Santarpia GW, et al.
Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska
Medical Center. medRxiv. 2020.
27. Guo Z, Wang Z, Zhang S, Li X, Li L, Li C, et al. Aerosol and Surface Distribution of Severe
Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020. Emerging
infectious diseases. 2020;26(7).
15
28. Chia PY, Coleman KK, Tan YK, Ong SWX, Gum M, Lau SK, et al. Detection of Air and
Surface Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in
Hospital Rooms of Infected Patients. medRxiv. 2020.
29. Liu Y, Ning Z, Chen Y, Guo M, Liu Y, Gali NK, et al. Aerodynamic characteristics and RNA
concentration of SARS-CoV-2 aerosol in Wuhan hospitals during COVID-19 outbreak. bioRxiv.
2020.
30. van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et
al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. New England
Journal of Medicine. 2020.
31. MacIntyre CR, Chughtai AA, Seale H, Richards GA, Davidson PM. Respiratory protection
for healthcare workers treating Ebola virus disease (EVD): Are facemasks sufficient to meet
occupational health and safety obligations? Int J Nurs Stud. 2014;51(11):1421-6.
32. MacIntyre CR, Chughtai AA, Seale H, Richards GA, Davidson PM. Uncertainty, risk
analysis and change for Ebola personal protective equipment guidelines. Int J Nurs Stud.
2014;52(5):899-903.
33. Macintyre R, Chughtai A, Tham CD, Seale H. BMJ (Clinical research ed) [Internet]2020.
[cited 2020].
34. Johnson D, Druce JD, Birch C, Grayson ML. A quantitative assessment of the efficacy of
surgical and N95 masks to filter influenza virus in patients with acute influenza infection.
Clinical Infectious Diseases. 2009;49(2):275-7.
35. MacIntyre CR, Zhang Y, Chughtai AA, Seale H, Zhang D, Chu Y, et al. Cluster randomised
controlled trial to examine medical mask use as source control for people with respiratory
illness. BMJ Open.6(12):e012330.
36. Canini L, Andreoletti L, Ferrari P, D'Angelo R, Blanchon T, Lemaitre M, et al. Surgical
mask to prevent influenza transmission in households: a cluster randomized trial. PLoS ONE
[Electronic Resource].5(11):e13998.
37. Barasheed O, Almasri N, Badahdah AM, Heron L, Taylor J, McPhee K, et al. Pilot
Randomised Controlled Trial to Test Effectiveness of Facemasks in Preventing Influenza-like
Illness Transmission among Australian Hajj Pilgrims in 2011. Infectious Disorders - Drug
Targets.14(2):110-6.
38. Leung NH, Chu DK, Shiu EY, Chan K-H, McDevitt JJ, Hau BJ, et al. Respiratory virus
shedding in exhaled breath and efficacy of face masks. Nature Medicine. 2020:1-5.
39. MacIntyre CR, Chughtai AA, Rahman B, Peng Y, Zhang Y, Seale H, et al. The efficacy of
medical masks and respirators against respiratory infection in healthcare workers. Influenza
and other respiratory viruses. 2017;11(6):511-7.
40. Cowling BJ, Zhou Y, Ip DK, Leung GM, Aiello AE. Face masks to prevent transmission of
influenza virus: a systematic review. Epidemiology and infection. 2010;138(4):449-56.
41. Bin-Reza F, Lopez Chavarrias V, Nicoll A, Chamberland ME. The use of masks and
respirators to prevent transmission of influenza: a systematic review of the scientific evidence.
Influenza and other respiratory viruses. 2012;6(4):257-67.
42. Gralton J, McLaws ML. Protecting healthcare workers from pandemic influenza: N95 or
surgical masks? Critical care medicine. 2010;38(2):657-67.
16
43. Gamage B, Moore D, Copes R, Yassi A, Bryce E. Protecting health care workers from
SARS and other respiratory pathogens: a review of the infection control literature. American
journal of infection control. 2005;33(2):114-21.
44. Jefferson T, Del Mar C, Dooley L, Ferroni E, Al-Ansary LA, Bawazeer GA, et al. Physical
interventions to interrupt or reduce the spread of respiratory viruses: systematic review. BMJ
(Clinical research ed). 2009;339:b3675.
45. Jefferson T, Del Mar CB, Dooley L, Ferroni E, Al-Ansary LA, Bawazeer GA, et al. Physical
interventions to interrupt or reduce the spread of respiratory viruses. The Cochrane database
of systematic reviews. 2011(7):CD006207.
46. Jefferson T, Foxlee R, Del Mar C, Dooley L, Ferroni E, Hewak B, et al. Physical
interventions to interrupt or reduce the spread of respiratory viruses: systematic review. BMJ
(Clinical research ed). 2008;336(7635):77-80.
47. Aledort JE, Lurie N, Wasserman J, Bozzette SA. Non-pharmaceutical public health
interventions for pandemic influenza: an evaluation of the evidence base. BMC public health.
2007;7:208.
48. Lee KM, Shukla VK, Clark M, Mierzwinski-Urban M, Pessoa-Silva CL, Conly J. Physical
Interventions to Interrupt or Reduce the Spread of Respiratory Viruses - Resource Use
Implications: A Systematic Review. Ottawa ON: 2011 Cadth.; 2011 Dec.
49. Verbeek JH, Rajamaki B, Ijaz S, Tikka C, Ruotsalainen JH, Edmond MB, et al. Personal
protective equipment for preventing highly infectious diseases due to exposure to
contaminated body fluids in healthcare staff. Cochrane Database of Systematic Reviews.
2019(7).
50. Bahl P, Doolan C, de Silva C, Chughtai AA, Bourouiba L, MacIntyre CR. Airborne or
droplet precautions for health workers treating COVID-19? The Journal of infectious diseases.
2020.
51. Keeley AJ, Evans C, Colton H, Ankcorn M, Cope A, Bennett T, et al. Roll-out of SARS-CoV-
2 testing for healthcare workers at a large NHS Foundation Trust in the United Kingdom, March
2020. Eurosurveillance. 2020;25(14):2000433.
52. Zhan M, Qin Y, Xue X, Zhu S. Death from Covid-19 of 23 Health Care Workers in China.
New England Journal of Medicine. 2020.
53. He X, Lau EH, Wu P, Deng X, Wang J, Hao X, et al. Temporal dynamics in viral shedding
and transmissibility of COVID-19. medRxiv. 2020.
17
Figure 1
Figure 1: Search strategy and selection of papers
18
Table 1 Community mask trials
Author, year
N, country
Interventions
Results
Cowling 2008
198 Households
Hong Kong
Medical masks
Hand washing
Control
NS – this was a preliminary report of
the 2009 trial.
MacIntyre 2009
143 Households
Australia
Medical masks
P2 masks
Control
Masks/P2 protective if adherent
Cowling 2009
407 households
Hong Kong
Hand hygiene
Masks + hand hygiene
Control
Masks plus hand hygiene protective,
Hand hygiene alone not protective
Aiello 2010
1437 college students, United
States of America
Health education (HE)
HE + sanitizer
HE + sanitizer + masks
HE + sanitizer + masks protective
Hand hygiene alone not protective
Aiello 2012
1178 college students, United
Masks
Masks + hand hygiene protective
19
States of America
Masks + hand hygiene
Control
Hand hygiene alone not protective
Larson 2010
617 households, United States of
America
Health education (HE)
Hand hygiene + HE
Masks + hand hygiene +HE
Masks + hand hygiene protective
Hand hygiene or HE alone not
protective
Simmerman 2011
465 index patients and their
families, Thailand
Hand hygiene
Masks + hand hygiene
Control
No significant difference in
confirmed influenza infection
Suess 2012
84 index cases and 218 household
contacts, Germany
Masks
Masks + hand hygiene
Control
Both intervention groups together
protective in compliant users together
protective compared to control
if used within 36 hours
20
Table 2: Trials of mask and respirator use by health care workers
Author, year
N healthcare workers,
Country
Interventions
Results
Jacobs 2009
32
Japan
Medical masks
Control
NS
Loeb 2009
446
Canada
Medical masks, targeted N95
NS
MacIntyre 2011
1441
China
Masks
N95 respirators, fit tested
N95 respirators, non-fit tested
Control
Continuous N95 protective against
clinical, viral and bacterial (25)
endpoints
MacIntyre 2013
1669
China
Medical Mask
N95 (continuous)
N95 (targeted)
Continuous N95 protective
No difference between targeted N95
and medical masks
MacIntyre 2015
1607
Vietnam
Medical masks, cloth masks, control
Medical masks protective or
Cloth masks increase risk of infection
21
Radonovich 2019
2862
United States of America
Medical masks, targeted
N95 (when 2m from confirmed
respiratory infection) in
Outpatient setting.
No significant difference between
Masks and targeted N95
22
Table 3: Trials of Masks used by a sick patient as source control
Author, year
N, country
Interventions
Results
Johnson 2009
9 subjects with confirmed
influenza, Australia
Medical mask
N95
(participants coughed 5 times onto a Petri dish
wearing each device)
NS - Surgical and N95 masks were
equally effective in preventing
the spread of PCR-detectable
influenza
Canini 2010
105 index cases and 306
household contacts, France
Medical mask
Control
No significant difference,
but trial terminated early
MacIntyre 2016
245 index cases and 597
household contacts,
Medical mask worn by sick case
Control (no mask) Household contacts
Followed for infection.
Mask protective if worn
Barasheed 2014
Hajj Setting. 22 tents were
randomised to ‘mask’ (n=12)
or ‘control’ (n=10)
75 pilgrims in ‘mask’ and 89
Mask and control
Less ILI among the contacts of mask users compared
to the control tents (31% versus 53%, p= 0.04).
Laboratory results did not show any difference
between the two groups
23
in ‘control’ group
Saudi Arabia
Leung 2020 Experimental study of 246 subjects 111 (90%) were infected by human (seasonal) coronavirus
Randomised to surgical mask and Coronavirus found in exhaled breath of no-mask subjects but not in
No mask. Mask wearers. More virus was found in fine aerosols than large droplets
