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Exercise after influenza or COVID-19 vaccination increases serum antibody without an increase in side effects

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Vaccination is an effective public health measure, yet vaccine efficacy varies across different populations. Adjuvants improve vaccine efficacy but often increase reactogenicity. An unconventional behavioral "adjuvant" is physical exercise at the time of vaccination. Here, in separate experiments, we examined the effect of 90-minute light- to moderate-intensity cycle ergometer or outdoor walk/jog aerobic exercise performed once after immunization on serum antibody response to three different vaccines (2009 pandemic influenza H1N1, seasonal influenza, and COVID-19). Exercise took place after influenza vaccination or after the first dose of Pfizer-BioNTech COVID-19 vaccine. A mouse model of influenza A immunization was used to examine the effect of exercise on antibody response and the role of IFNα as a potential mechanism by treating mice with anti-IFNα antibody. The results show that 90 minutes of exercise consistently increased serum antibody to each vaccine four weeks post-immunization, and IFNα may partially contribute to the exercise-related benefit. Exercise did not increase side effects after the COVID-19 vaccination. These findings suggest that adults who exercise regularly may increase antibody response to influenza or COVID-19 vaccine by performing a single session of light- to moderate-intensity exercise post-immunization.
Serum IgG response to seasonal influenza vaccine. 2a & 2b. Serum antibody level assessed as optical density at 405 nm by ELISA. Serum dilution series indicate assay level of detectability for H1N1 at OD = 224. A significant main effect of time was observed as antibody increased in response to vaccination (main effect of time, p < 0.0001, F = 111.59). 90-minute exercise increased antibody response (time * exercise interaction, p < 0.001, F = 10.5, df = 24, η 2 partial = 0.489; main effect of exercise, p = 0.027, F = 4.379, df = 24, η 2 partial = 0.277; post-hoc analysis (Sidak)) with no difference between no-ex and 45-min ex or 90-min ex and 45-min ex). No significant effect of age. 2c. Fold change in antibody level calculated relative to pre-immunization, * indicates greater fold change in 90-min exercise condition than either no-ex or 45-min exercise (main effect of exercise, p = 0.005, F = 7.13, df = 24, η 2 partial = 0.387, post hoc analysis (Sidak) with no difference between no-ex and 45-min ex, and 90-min ex > 45-min ex (p = 0.001), 90-min ex > no-ex (p = 0.005). 2d & 2e. Serum antibody level assessed as optical density at 405 nm by ELISA. Serum dilution series indicate assay level of detectability for H3N2 at OD = 219. In the overall model, a significant main effect of time as antibody increased in response to vaccination (main effect of time, p < 0.001, F = 31.7, df = 25). There was a significant time by exercise interactions (p = 0.021, F = 3.2, df = 25, η 2 partial = 0.235, and the 90-minute exercise was associated with increased antibody response (* main effect of exercise, p = 0.014, F = 5.217, df = 25, η 2 partial = 0.332) post-hoc analysis (Sidak) with no difference between no-ex and 45-min ex, but 90-min was significantly greater than no ex (p = 0.015) and also>45-min ex, (p = 0.04). 2f. Fold change in antibody titer calculated relative to pre-immunization. A trend toward main effect of exercise was noted (p = 0.07, F = 2.93, df = 25,
… 
Mouse Serum anti-Influenza A/PR/8/34 IgG, IgG1, or IgG2a response to vaccination following varying durations of exercise, and the role of IFNα (mice). 4a. Serum was collected at either 2 weeks or 4 weeks post-immunization (separate mice at 2 weeks and 4 weeks). No significant effect of exercise at 2 weeks. At 4 weeks of exercise, exercise treatment altered antibody response (overall significant effect of exercise, p = 0.044, F = 3.046, df = 34, η 2 partial = 0.233) and post hoc analysis results indicated serum IgG in mice completing 90 min of exercise > no ex (*p = 0.004). 4b. Serum anti-influenza IgG1 assessed at 4 weeks post-immunization. There was a statistical trend (overall effect of exercise, p = 0.09, F = 2.92, df = 34, η 2 partial = 0.168) towards a difference between groups. 4c. Total anti-influenza serum IgG was measured four-weeks post-immunization. Anti-IFNα antibody-treated mice had significantly less IgG but exercise increased IgG in both anti-IFNα treated mice and mice treated with irrelevant antibody (main effect of antibody, * p < 0.001, F = 28.3, df = 38, η 2 partial = 0.447 ; main effect of exercise, p = 0.002, F = 11.5, df = 38, η 2 partial = 0.247). There was no significant exercise group * anti-IFNα interaction, p = 0.128). 4d & 4e. Anti-influenza serum IgG1 (6b) or IgG2a (6c) were measured at four weeks post-immunization. Without IFNα, antibody response was significantly reduced for IgG1 (main effect of IFNα antibody treatment, p < 0.001, F = 24.5, df = 38, η 2 partial = 0.447) and exercise treatment significantly increased IgG1 (p < 0.001, F = 23.5, df = 38, η 2 partial = 0.402), and there was a trend towards an anti-IFNα antibody by exercise treatment interaction (p = 0.06). With respect to IgG2a there was a significant interaction between exercise treatment and anti-IFNα antibody (exercise * antibody interaction, p = 0.014, F = 6.63, df = 38, η 2 partial = 0.159) implying the exercise effect was not consistent across antibody treatment. For IgG2a, effect of exercise (p < 0.001, F = 23.73, df = 38, η 2 partial = 0.404) and IFNα antibody treatment, p < 0.001, F = 31.6, df = 38, η 2 partial = 0.475). 4f. The significant interaction for IgG2a (from 4f) is shown in a line graph format.
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Brain, Behavior, and Immunity 102 (2022) 1–10
Available online 5 February 2022
0889-1591/© 2022 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Full-length Article
Exercise after inuenza or COVID-19 vaccination increases serum antibody
without an increase in side effects
Justus Hallam
a
,
b
, Tyanez Jones
c
, Jessica Alley
a
,
b
, Marian L. Kohut
a
,
b
,
c
,
*
a
Department of Kinesiology, Iowa State University, Ames, IA, USA
b
Program of Immunobiology, Iowa State University, Ames, IA, USA
c
Nanovaccine Institute, Iowa State University, Ames, IA, USA
ARTICLE INFO
Keywords:
Exercise
Vaccine
Inuenza
COVID-19
ABSTRACT
Vaccination is an effective public health measure, yet vaccine efcacy varies across different populations. Ad-
juvants improve vaccine efcacy but often increase reactogenicity. An unconventional behavioral adjuvantis
physical exercise at the time of vaccination. Here, in separate experiments, we examined the effect of 90-minute
light- to moderate-intensity cycle ergometer or outdoor walk/jog aerobic exercise performed once after immu-
nization on serum antibody response to three different vaccines (2009 pandemic inuenza H1N1, seasonal
inuenza, and COVID-19). Exercise took place after inuenza vaccination or after the rst dose of Pzer-
BioNTech COVID-19 vaccine. A mouse model of inuenza A immunization was used to examine the effect of
exercise on antibody response and the role of IFN
α
as a potential mechanism by treating mice with anti-IFN
α
antibody. The results show that 90 min of exercise consistently increased serum antibody to each vaccine four
weeks post-immunization, and IFN
α
may partially contribute to the exercise-related benet. Exercise did not
increase side effects after the COVID-19 vaccination. These ndings suggest that adults who exercise regularly
may increase antibody response to inuenza or COVID-19 vaccine by performing a single session of light- to
moderate-intensity exercise post-immunization.
1. Introduction
Physical exercise performed near the time of immunization may in-
crease antibody response to vaccination. Several studies have reported
such ndings, demonstrating that exercise preceding immunization
improved antibody response (Edwards et al. 2012; Edwards et al. 2006;
Edwards, et al. 2007; Ranadive et al. 2014). One explanation given for
these results is that exercise may act as an acute stressor. There are
examples in the literature that demonstrate that acute stress may in-
crease antibody response when applied before immunization (Edwards,
et al. 2008; Edwards et al. 2006; Silberman et al. 2003). It has also been
suggested that eccentric exercise produces a local inammatory
response, potentially resulting in greater antigen-presenting cell acti-
vation. In some studies, eccentric exercise before vaccination increased
antibody response (Edwards, et al. 2007). As another possibility, it is
recognized that an increase in serum IL-6 accompanies exercise (Reih-
mane and Dela, 2014; Vasconcelos and Salla, 2018), and the exercise-
associated change in IL-6 may be another mechanism by which exer-
cise may enhance antibody response (Edwards et al., 2006). Studies
show the administration of IL-6 at the time of inuenza immunization
increases IgG, mediated indirectly by CD4
+
T cells (Dienz, et al. 2009).
IL-6 has a role in T follicular helper (TFH) CD4
+
T cell differentiation
(Choi, et al. 2013; Eto, et al. 2011), permitting germinal center TFH cells
to receive continued T-cell receptor signaling (Papillion, et al. 2019).
Therefore, evidence supports the possibility that increased IL-6 at the
time of exercise could contribute to exercise-induced increases in serum
antibody. However, a consistent association between IL and 6, exercise,
and antibody response to vaccine has not been observed, and as a result,
the mechanisms to explain the association between exercise and vaccine
response remain speculative.
The current research on exercise and vaccination shows promising
ndings in several studies (Edwards, et al. 2006; Edwards, et al. 2007;
Edwards, et al. 2008; Ranadive, et al. 2014), but signicant challenges
remain. For example, the results across studies are inconsistent, as some
studies demonstrate no benet of exercise (Bohn-Goldbaum, et al. 2020;
Bohn-Goldbaum, et al. 2019; Bruunsgaard, et al. 1997; Campbell, et al.
2010; Long, et al. 2012). Others report an exercise-related response to
one antigen in a vaccine but no effect on the response to other antigens
* Corresponding author at: Department of Kinesiology, Iowa State University, 5203 ATRB, Ames, IA 50011-4008, USA.
E-mail address: mkohut@iastate.edu (M.L. Kohut).
Contents lists available at ScienceDirect
Brain Behavior and Immunity
journal homepage: www.elsevier.com/locate/ybrbi
https://doi.org/10.1016/j.bbi.2022.02.005
Received 26 October 2021; Received in revised form 27 January 2022; Accepted 1 February 2022
Brain Behavior and Immunity 102 (2022) 1–10
2
contained in the same vaccine (Edwards, et al. 2006; Ranadive, et al.
2014). Ideally, an effective adjuvant would be expected to demonstrate
a consistent enhancement across all antigens in a vaccine. The theory
that eccentric exercise might elicit an inammatory response to boost
antibody has not held up consistently, given the ndings showing no
benet of eccentric exercise or a difference only for one sex (Campbell,
et al. 2010; Edwards, et al. 2007). Given the inconsistencies across
studies, it has been suggested that an effect of exercise may be observed
only under conditions in which antigen dose is low, or participants tend
towards a reduced antibody response (Edwards, et al. 2012). This
interpretation of existing ndings implies that exercise effects are small
in magnitude compared to the large immune stimulus from a vaccine,
and therefore may be difcult to detect.
In order to advance the concept of exercise as a vaccine behavioral
adjuvant, with translational public health relevance, it is essential to
dene the exercise parameters that consistently result in enhanced
serum antibody. It is also critical to identify the vaccine platforms and
pathogens for which an effect of exercise may be present. In this study,
we evaluated the effect of standardized aerobic exercise administered
after immunization in contrast to other studies that focused on exercise
prior to vaccine. In the stress and immunity literature, a stressor applied
after immunization has been shown to enhance antibody response to
vaccination (Karp, et al. 2000; Wood, et al. 1993). Therefore, we eval-
uated the effect of exercise on antibody response when exercise was
administered after immunization rather than before.
Additional rationale for selecting 90 min of exercise was based partly
on unpublished ndings demonstrating that 90 min of exercise results in
a signicant increase in the type I interferon, interferon-alpha (IFN
α
)
production by plasmacytoid dendritic cells upon activation (Supplement
Table S1). Type I IFNs promote dendritic cell activation (Montoya, et al.
2002), increase antibody production, promote class switching (Le Bon,
et al. 2001), and may have a direct stimulatory effect on B cells and T
cells (Le Bon, et al. 2006), Adjuvants that induce type I IFN potently
increase antibody response to vaccination (Junkins, et al. 2018).
Therefore, in addition to studies with human participants, a rodent
model was included. In the rodent experiments, anti-IFN
α
antibody was
used to block IFN
α
at the time of immunization to evaluate whether
IFN
α
may be one mechanism contributing to the exercise-induced
enhancement of antibody response. We also evaluated 45 min of exer-
cise in some experiments involving young and aged adults as aged adults
may be more readily able to complete 45 min of light-intensity exercise
instead of 90 min. We examined the role of exercise in response to a
novelH1N1 antigen with vaccine response to 2009 H1N1 Pandemic
(H1N1pdm09) virus and the response to a trivalent seasonal inuenza
virus in which neither type of inuenza A would be considered novel.
Finally, in early studies with human participants, we examined the in-
uence of exercise on antibody response to an mRNA-based vaccine,
PzerBioNTech BNT162b2, against the disease caused by the novel
coronavirus SARS-CoV-2 (COVID-19), using the same exercise approach
that we found to be effective in inuenza experiments. As the inuenza
vaccine platforms consisted of split-virus preparations and the P-
zerBioNTech BNT162b2 vaccine was based on an mRNA platform, we
compared the effect of exercise across different vaccine platforms. Ex-
ercise has been proposed as a potential behavioraladjuvant for
COVID-19 immunization (Valenzuela, et al. 2021), and the experiments
conducted here investigated that possibility.
2. Methods
For all experiments involving human subjects, participants were
recruited by yers posted in the local community as well as by email sent
to university staff, students, or community organizations and businesses
that schedule group vaccination clinics.
2.1. Inuenza vaccine research participants
A total of 20 participants were enrolled in the monovalent Inuenza
A/California/7/09 H1N1 vaccine experiment, and 16 were included in
the nal analysis (see Supplement Fig. 1 CONSORT diagram). A total of
28 participants were enrolled in the trivalent seasonal inuenza vaccine
experiment, and 26 were included in the nal analysis (see Supplement
Fig. 2 CONSORT diagram). Individuals were excluded if they were:
taking medications for psychological disorders or medications that
altered immune variables of interest (e.g., oral corticosteroids); had any
medical condition that may directly impact immune outcomes,
including autoimmune disorders; or were unable to perform the pre-
scribed exercise safely. Participants were included if they had been
exercising regularly for at least the previous six months and met the
criteria set forth for moderate-intensity exercise in accordance with
American College of Sports Medicine Guidelines (American College of
Sports Medicine, 2018). In the rst experiment, participants were
immunized with a monovalent vaccine of a novel strain (single antigen
A/California/7/09 Inuenza H1N1, pdm09), hereafter referred to as
monovalent. In a second experiment, participants were vaccinated
with the trivalent inuenza vaccine ((Inuenza A/California/7/09, A/
Perth /16/2009, B/Brisbane/60/2008), termed seasonalvaccine. All
participants received the current inuenza Vaccine Information State-
ment and were asked to report any concerning side effects to study
personnel. The Institutional Review Board approved all procedures at
Iowa State University.
2.2. COVID-19 vaccine research participants
A total of 36 individuals that received the Pzer BNT162b2 (Pzer-
BioNTech COVID-19 Vaccine) between March 2021-June 2021 were
enrolled in the study (see Supplement Fig. 3 CONSORT diagram). Data
from eight participants who were possibly previously infected with
SARS-CoV-2 based on higher pre-immunization antibody levels and a
larger magnitude of change in response to the rst vaccine was reported
but not considered part of the primary analysis. Participants were
included in the study if they regularly participated in moderate or
vigorous-intensity exercise two or more times a week, with, on average,
at least one session lasting 50 min or longer. Participation in the study
followed the American College of Sports Medicine recommendations for
preparticipation health screening (Riebe, et al. 2015). Individuals were
excluded if they had an immune condition that would be expected to
impact the variables of interest or if they were taking a medication that
signicantly alters immune response. Individuals who were not preg-
nant, who planned to receive the COVID-19 vaccine, and who were
willing to donate blood were included in the study.
2.3. Psychosocial surveys for inuenza experiments
All participants in the inuenza vaccine experiments completed
several psychosocial surveys to determine whether there was an asso-
ciation between antibody response to the vaccine and psychosocial
factors. All participants completed the following surveys: Perceived
Stress Scale (PSS) (Cohen, et al. 1983), Sense of Coherence (SOC)
(Antonovsky, 1993), and Prole of Mood States (POMS) (McNair, et al.
1992).
2.4. Blood Collection, Vaccination, and timeline
Blood was taken from an antecubital vein (30 ml) in subjects just
before immunization with either the monovalent or seasonal inuenza
vaccine. Blood was collected at two weeks and four weeks post-
immunization.
A pre-immunization blood sample was collected within the week
preceding the COVID-19 vaccination. After the rst Pzer BioNTech
COVID-19 vaccine was administered, subjects returned two weeks later
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
3
for blood collection. The second dose of vaccine was given three weeks
after the rst vaccine dose. An additional blood sample was collected
one week following the second Pzer BioNTech COVID-19 vaccine (1
week post dose 2). All participants received side effect report forms
listing the side effects described on the Pzer BioNTech emergency use
authorization. Side effects were recorded every 24 h for the rst 72 h
after each vaccine by placing a check next to each side effect if present. A
score of 1 was given each day a given side effect was recorded by the
participant. Therefore, scores ranged from 0 (not present on any day) to
3 (present on each of the three days following the vaccine) for each side
effect listed on the emergency use authorization form.
2.5. Exercise conditions
In the experiment in which monovalent H1N1 vaccine was admin-
istered, subjects were randomly assigned to a light- to moderate-
intensity exercise group (90 min) or no exercise control group. If ran-
domized to exercise, participants began the exercise session within 30
min of receiving the single antigen vaccine. If assigned to control, the
participants started a sedentary period within 30 min of vaccination.
The sedentary period consisted of sitting while watching videos for 90
min. Adults randomized to exercise performed 90 min of exercise on a
cycle ergometer at 6070% of estimated maximal heart rate (HR max)
with the range calculated as [(220 age) ×0.6] to [(220-age) ×0.7],
typically corresponding to an intensity perceived as light to somewhat
hard based on the Rating of Perceived Exertion (RPE) Borg 620 scale
(Borg, 1982). After a 10-minute warm-up period, the cycling rate and
workload were adjusted to maintain heart rate in the appropriate range.
Heart rate and RPE (Borg 620 scale) were assessed every 10 min, and
water was available for the participant.
In the experiment in which seasonal vaccine was administered,
young (age 1833) subjects were randomly assigned to one of three
groups: no exercise, 45 min of exercise, or 90 min of exercise, whereas
aged subjects (age 6287) were randomly assigned to one of two groups:
no exercise, or 45 min of exercise. The exercise or rest period
commenced within 30 min after receiving the seasonal inuenza vac-
cine. The same exercise intensity was adhered to throughout exercise
(6070% of age-estimated HR max on a cycle ergometer). Heart rate and
RPE were assessed every 10 min. Participants assigned to the no exercise
condition remained sedentary for 90 min post-vaccine, seated watching
videos.
In the experiments involving the COVID-19 vaccine, participants
were randomly assigned to either 90 min of exercise or instructed to go
about their daily routine but avoid exercise on the day of the rst
vaccination. All participants were asked to avoid exercise on the day the
second vaccine dose was given. Exercise took place outdoors at the
location where participants were vaccinated to limit SARS-CoV-2
infection risk for participants and study personnel. Study personnel
identied a safe walking/jogging route, and routes were designed to
monitor heart rate and RPE approximately every 10 min. An exercise
heart rate zone of approximately 120140 beats per minute was targeted
as this range was consistent with the average heart rate range performed
at the target zone of 6070% of HR max in the inuenza vaccine studies.
As exercise took place outdoors to minimize risk of SARS-CoV-2 infec-
tion, it was not possible to precisely control heart rates as compared to
the inuenza vaccine studies in which a cycle ergometer was used to set
a workload. Therefore, although target heart rate was approximately
equal to the target zone of 6070% of HR max as in the inuenza vaccine
experiments, there was slightly more variability due to terrain condi-
tions. The exercise intensity was also monitored by RPE and consistent
with the inuenza vaccine studies in which target RPE was light to
somewhat hard. RPE was also used to adjust exercise intensity for any
participants treated with beta-blocker medications.
2.6. Serum antibody Detection assays (Human Sera)
After collection, blood sat at room temperature for 45 min until
clotted, was then centrifuged at 180 ×g, and was frozen at 80 C
o
until
subsequent measurement of anti-inuenza antibodies by ELISA. Samples
from the same individual for all time points were run together on the
same plate to minimize variability. Briey, for A/California/7/09, plates
were coated with 1 µg/ml hemagglutinin peptide in carbonate coating
buffer, followed by overnight incubation. For A/Perth/16/2009, plates
were coated with 256 hemagglutination (HA) units/ml, followed by
overnight incubation. Plates were washed with phosphate-buffered sa-
line (PBS) containing 0.05% Tween 20 between each step. Dilutions of
serum were added to the wells in duplicate with an optimal dilution of
1:200 for IgG based on preliminary experiments in which the optimal
dilution yielding a difference from pre-immunization values was iden-
tied. After overnight incubation, AP-conjugated goat anti-human IgG
(Southern Biotech) was added at 1:100 dilution. Phosphatase substrate
(Sigma) was added, and optical density (OD) was assessed at 405 nm on
a Fluostar plate reader. Data is shown as OD or fold change in OD from
pre-immunization to post-immunization time points. The OD repre-
senting the level of detectability for each assay is indicated in the
appropriate gure legend. This endpoint was calculated by a dilution
series carried out in a subset of participants to determine the OD at the
titer at which subsequent dilutions no longer detected a change in OD.
The detectable limits were calculated separately for each vaccine anti-
gen and in the appropriate group of participants. For experiments
involving COVID-19 vaccination, antibody level was measured using
GenScript SARS-CoV-2 Spike S1-RBD IgG&IgM ELISA Detection Kit. The
manufacturers directions were followed. Briey, serum was diluted
1:100 and the HRP-conjugated mouse anti-human IgG Fc was added to
the plate to detect anti-RBD IgG antibody. Banked pre-pandemic serum
was used as a negative control.
2.7. Mice, exercise conditions, vaccination, and IFN
α
antibody treatment
In all experiments, male BALB/c mice at 10 to 12 weeks of age
(Charles River Labs) were used. First, we compared different durations
of moderate-intensity exercise to determine the extent to which exercise
duration altered antibody response to intramuscular injection of inu-
enza vaccine. These experiments were replicated to conrm 90 min as
the duration in which increased antibody to vaccination was observed.
Next, we tested the hypothesis that IFN
α
mediates exercise-induced
changes in serum antibody concentration by administering anti-IFN
α
antibody to a subset of mice. Vaccinated mice in both experiments
received 50
μ
L of Binary ethyleneimine inactivated A/PR/8/34 virus
(512 HA units) administered intramuscularly into the quadriceps. Saline
control mice received 50 µL of saline and did not exercise. All mice were
acclimated to the treadmill running for three days in the week preceding
experiments by exposing mice to gradually increasing speeds on a
motorized treadmill for 1015 min. All studies were performed ac-
cording to Institutional Animal Care and Use Committee guidelines at
Iowa State University and within the guidelines set by the NIH for the
care and use of laboratory animals.
In the rst experiment, thirty-eight BALB/c mice were randomly
assigned to one of four treatment groups (810 mice per group): no
exercise, or moderate-intensity exercise for 45 min post-immunization,
90 min post-immunization, or 3 h post-immunization. In a subsequent
experiment, we tested the role of IFN
α
as a mechanism by which exercise
may inuence antibody response to vaccine. Mice were randomly
assigned to one of four groups (910 mice per group): no exercise, no
exercise +anti-IFN
α
antibody, 90 min moderate-intensity exercise, 90
min moderate-intensity exercise +anti-IFN
α
antibody. The anti-IFN
α
treatment consisted of daily injection with 20 µg/mouse of rat IgG1 anti-
mouse IFN
α
, clone RMMA-1 (PBL Interferon Source) diluted in saline
containing 0.01% bovine serum albumin (BSA). Antibody administra-
tion began the day before vaccination (day 1) and continued until day
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
4
three post-immunization. Mice that did not receive anti-IFN
α
treatment
were injected with 20 µg/mouse of an irrelevant antibody, rat IgG1, at
the same dose and time of day as anti-IFN
α
treated mice. The 90-minute
exercise duration was selected based upon results from the initial ex-
periments, which demonstrated this exercise duration resulted in
increased antibody response to vaccine.
Mice began their respective exercise protocols within 15 min
following vaccination. Mice performed exercise on a treadmill at a speed
of 15 m/min, which has been shown to be moderate intensity (Fernando,
et al. 1993; Hoydal, et al. 2007). No-exercise mice were placed in
housing cages afxed to the top of the treadmill to mimic stressors
associated with the treadmill environment (noise, vibration) as closely
as possible. All mice were acclimated to the treadmill environment on
two separate occasions before immunization.
2.8. Serum antibody response to vaccine (mouse sera)
Blood was collected from all mice at two weeks post-immunization or
four weeks post-immunization. Blood was allowed to clot at room
temperature and then centrifuged at 180 ×g for 15 min. Serum was
collected and frozen at 80 C until subsequent measurement of IgG,
IgG1, and IgG2a anti-inuenza antibodies by ELISA. Briey, plates were
coated overnight at 4C with inuenza virus A/PR/8/34 diluted in
carbonate coating buffer (pH 9.6) at a 200 HA units/ml concentration
for anti-inuenza IgG, IgG1, and IgG2a. The wells were blocked with
0.1% BSA solution at 37 C for one hour. Plates were washed three times
with PBS containing 0.05% Tween 20 between each step. Diluted serum
(1:50 for IgG and 1:5 for IgG1 or IgG2a) was added to the wells and
incubated for 3 h at 37 C. These dilutions were chosen based on pre-
liminary assay optimization (data not shown). After incubation, AP-
conjugated rat anti-mouse IgG, IgG1, or IgG2a were added (at 1:100
dilution for IgG and 1:10 for IgG1 and IgG2a), then plates were incu-
bated overnight at 4 C. Finally, phosphatase substrate (4-Nitrophenyl
phosphate disodium salt hexahydrate, (Sigma) was added, and OD was
assessed at 405 nm at 30 min (IgG) and 50 min (IgG1, IgG2a) using a
Fluostar plate reader.
2.9. Statistical analysis
Statistics for all surveys, exercise data, and ELISA results in experi-
ments involving human participants were calculated using SPSS statis-
tical software (PASW/IBM Inc.) to perform ANOVAs. A mixed ANOVA
(exercise treatment * time) was used to compare serum anti-inuenza
immunoglobulins (IgG) to the different exercise durations post-
vaccination (either direct OD readings at respective serum dilutions or
fold change in OD relative to pre-immunization level, as indicated in
results). In experiments that included different age groups (seasonal
Inuenza vaccine), age and exercise were included in the model. In the
experiment with a wide range of ages (COVID-19 vaccine), initial ana-
lyses examined the effect of exercise only. A secondary analysis was
performed in which the top quartile for age was used to dene a middle-
aged population (ages 4462) compared with participants considered
young adults (ages 1843). Pearson correlations were used to compare
psychological survey outcomes and antibody response to the Inuenza
A/California/7/09 H1N1 antigen, combining the monovalent and sea-
sonal vaccine results. All data are reported as mean ±standard error of
the mean (SEM) unless otherwise indicated. In mouse experiments, a
one-way ANOVA was used to evaluate the effect of exercise duration on
antibody response followed by post-hoc analysis (Sidak). A two-way
ANOVA (exercise group and anti-IFN
α
antibody treatment group) was
used to compare antibody response in experiments to test the role of
IFN
α
as a mechanism by which exercise may impact antibody response.
Values of p <0.05 were considered statistically signicant, while values
of 0.05 <p <0.1 were considered a statistical trend.
3. Results
3.1. Demographics and response to exercise
Age, exercise heart rate, and RPE data are shown in Supplement
Table 2 (S2). There were no age differences between non-exercisers or
exercise treatment groups within each separate vaccine experiment.
Within the inuenza seasonal vaccine experiment, heart rate among
young participants was not different between the 45- or 90-minute ex-
ercise condition, but RPE in the 90-minute condition was slightly greater
than the 45-minute condition.
3.2. Antibody response to monovalent or seasonal inuenza vaccine,
effect of exercise, and association with psychosocial factors
The serum IgG response to monovalent H1N1 vaccine increased as
expected following vaccination (signicant main effect of time), as
shown in Fig. 1a. A signicant treatment by time interaction suggested
that the antibody response between the exercise group and no exercise
group responded differently over time with a greater response in the
exercise group (Fig. 1a). When results were calculated as fold change
relative to pre-immunization, a trend towards greater fold change in
antibody was observed in the exercise group relative to no exercise
(main effect of exercise, Fig. 1b). Individual antibody data for mono-
valent vaccine is also shown in Supplement Figure S4a-S4c. Antibody
response to seasonal inuenza vaccine was compared in young or aged
adults that exercised moderately for 45 min, 90 min (young only), or did
not exercise. The results show that anti-H1N1 serum IgG increased in
response to the vaccine as expected (signicant effect of time, Fig. 2a).
Over time, the change in antibody response differed between groups
(signicant time by exercise interaction), and the 90-minute exercise
condition resulted in greater serum antibody than no exercise. However,
antibody response in those assigned to the 45-minute exercise condition
was not different than no exercise in young or aged participants (Fig. 2a
and 2b, main effect of exercise, post-hoc analyses 90-min exercise >no-
ex). When data was calculated as fold change relative to pre-
immunization, the results were similar in that fold change of antibody
level in response to 90 min of exercise was signicantly greater than no-
exercise or 45 min of exercise (Fig. 2c), (main effect of exercise, 90-min
>no-exercise or 45-min ex in post-hoc analyses). There was no benet in
fold change in antibody level for the 45-minute exercise condition
relative to no exercise for either young or aged adults. The results con-
cerning anti-H3N2 antibody response as shown in Fig. 2d 2f are similar
to H1N1. Again, 90 min of exercise treatment resulted in greater anti-
body level (main effect of exercise, Fig. 2d), and as expected, antibody
increased in response to vaccination (main effect of time, Fig. 2d and
2e). The 45-minute exercise condition did not improve antibody
response in young or aged participants, and there was no effect of age on
antibody response. Individual data for the response to seasonal vaccine
are shown in Supplement Figures S5a-S5h.
Given that the same Inuenza A/California/7/09 H1N1 antigen was
present in the monovalent and seasonal vaccine experiments, we com-
bined the psychosocial survey data from these two experiments to
analyze associations between antibody and psychosocial factors. A
negative association between antibody titer and perceived stress and a
similar negative association between antibody level and total mood
disturbance were noted, but the correlations did not meet statistical
signicance (Supplement Figures 8a-8c). A positive association between
the Sense of Coherence score and antibody was observed, but again this
relationship did not meet statistical signicance.
3.3. Antibody response to Pzer BioNTech COVID-19 vaccine and effect
of exercise
Antibody to SARS-CoV-2 was not measured before enrollment.
Therefore, we could not determine which participants may have
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
5
experienced asymptomatic infection before immunization or experi-
enced an infection with COVID-19-like symptoms but did not have a
conrmed positive COVID antigen test. Upon analysis of antibody level
pre- and post-immunization, we noted that 8 of 36 participants were
possibly infected based upon >1.5 fold greater pre-immunization OD
value as compared those assumed to be not previously infected, and a
signicant increase in antibody level after the rst vaccine nearly
equivalent to the antibody level observed after the second dose in those
assumed to be not previously infected. Based on these criteria, the
antibody level of possibly infected participants was signicantly
higher at the pre-immunization time point and two weeks after the
initial vaccine (Fig. 3a). The nding that antibody titer in response to the
rst dose of vaccine is typically greater in previously infected as
compared to naïve individuals is a common nding in the literature,
whereas differences in antibody response between previously infected
relative to naïve may or may not be present in response to the second
Fig. 1. Serum IgG response to monovalent inuenza H1N1 vaccine. 1a. Serum anti-inuenza IgG shown as optical density at 405 nm by ELISA assay from serum samples
collected pre-immunization, two, or four-weeks post. Serum dilution series indicate assay level of detectability at OD =203. A signicant main effect of time (**p =
0.001, F =15.07), and a signicant time by treatment interaction between the no-exercise and 90-minute exercise condition (*p =0.04, F =3.68, df =15,
η
2
partial
=0.235) were found. 1b. Calculated fold change in antibody response, with a trend to main effect of exercise treatment (+p =0.059, F =4.36, df =15,
η
2
partial
=0.255).
Fig. 2. Serum IgG response to seasonal inuenza vaccine. 2a & 2b. Serum antibody level assessed as optical density at 405 nm by ELISA. Serum dilution series indicate
assay level of detectability for H1N1 at OD =224. A signicant main effect of time was observed as antibody increased in response to vaccination (main effect of
time, p <0.0001, F =111.59). 90-minute exercise increased antibody response (time * exercise interaction, p <0.001, F =10.5, df =24,
η
2
partial =0.489; main
effect of exercise, p =0.027, F =4.379, df =24,
η
2
partial =0.277; post-hoc analysis (Sidak)) with no difference between no-ex and 45-min ex or 90-min ex and 45-
min ex). No signicant effect of age. 2c. Fold change in antibody level calculated relative to pre-immunization, * indicates greater fold change in 90-min exercise
condition than either no-ex or 45-min exercise (main effect of exercise, p =0.005, F =7.13, df =24,
η
2
partial =0.387, post hoc analysis (Sidak) with no difference
between no-ex and 45-min ex, and 90-min ex >45-min ex (p =0.001), 90-min ex >no-ex (p =0.005). 2d & 2e. Serum antibody level assessed as optical density at
405 nm by ELISA. Serum dilution series indicate assay level of detectability for H3N2 at OD =219. In the overall model, a signicant main effect of time as antibody
increased in response to vaccination (main effect of time, p <0.001, F =31.7, df =25). There was a signicant time by exercise interactions (p =0.021, F =3.2, df =
25,
η
2
partial =0.235, and the 90-minute exercise was associated with increased antibody response (* main effect of exercise, p =0.014, F =5.217, df =25,
η
2
partial
=0.332) post-hoc analysis (Sidak) with no difference between no-ex and 45-min ex, but 90-min was signicantly greater than no ex (p =0.015) and also>45-min ex,
(p =0.04). 2f. Fold change in antibody titer calculated relative to pre-immunization. A trend toward main effect of exercise was noted (p =0.07, F =2.93, df =25,
η
2
partial =0.219).
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
6
vaccine (Ali et al., 2021, Ebinger, et al. 2021, Fraley, et al., 2021, Geers,
et al., 2021, Gobbi et al., 2021, Goel, et al., 2021, Krammer et al., 2021).
However, the presence of antibody to nucleocapsid protein can further
differentiate these populations, which was not measured in this study,
and this is a limitation in the method we used to dene possibly
infected. As the initial vaccination likely served as a second dose for
possibly infected participants, these participants were removed from the
primary data analysis because the fold change in antibody response
differed signicantly from participants who were assumed to be naive.
The serum anti-RBD IgG antibody level assessed over time shows a
signicant time by treatment interaction (Fig. 3b) with a greater in-
crease in the exercise group over time. When results are expressed as
fold change in antibody relative to pre-immunization, exercise partici-
pants have signicantly greater antibody (Fig. 3c). Individual data as
fold change or OD are shown in Supplement Figures S6a-S6c. We also
observed a signicant negative correlation between age and antibody
level at two weeks following the initial immunization and one week
following the second vaccine dose when antibody was measured either
as OD or fold change. The Pearson correlation between age and OD two
weeks post-immunization was 0.534, p =0.006; at one-week post-dose
2, the Pearson correlation between age and OD was 0.603, p =0.002.
Given the effect of age, the results of a secondary analysis in which age
group was included as a factor (young adult as 1843, middle-aged as
4464) showed a signicant interaction between age, exercise, and
antibody level over time (pre, 2 wk post, 1 wk post-dose 2; p =0.008, F
=5.38; graph not shown). When antibody was assessed as fold change
relative to pre-immunization, a similar pattern was observed with a
trend towards a signicant interaction between age, exercise, and fold
change in antibody (2 wk post, 1 wk post-dose 2; Fig. 3d). Middle-aged
participants had signicantly lower fold changes in antibody response
compared to young (Fig. 3d). Participants recorded side effects for three
days after receiving each vaccine. The side effect scores were not
signicantly different between 90-minute exercise participants
compared to no exercise (Supplement, Table S3). Reported side effects
on a percentage basis are also shown (Supplement, Table S4). Initial
ndings for the participants that were in the possibly infectedcategory
included only eight subjects, but this data is reported (n =5 no exercise,
n =3 exercise) (Supplement Figure S9).
Fig. 3. Serum anti-RBD IgG response to Pzer BioNTech COVID-19 vaccine 3a. SARS-CoV-2 Spike S1-RBD IgG from serum of participants categorized as possibly
infectedprior to immunization was signicantly greater at pre-immunization and at 2 wk after the initial vaccine, but not different at 1 wk post-dose 2 (main effect
of time, p <0.001, F =61.2, main effect of group, p <0.001, F =19.1, time by group interaction, p , F =19.6; and follow up one-way ANOVA to identify time points
of difference, * indicates difference at pre-immunization p <0.001, F =37.8; and * indicates difference at 2 wk post p <, 0.001, F =46.2). 3b. SARS-CoV-2 Spike S1-
RBD IgG as optical density (OD) in serum collected pre-immunization, 2 wk after initial vaccine or 1 wk after second vaccine dose (the second vaccine was
administered 3 weeks after the rst vaccine dose). * indicates signicant treatment group by time interaction (p =0.039, F =3.50, df =25,
η
2
partial =0.137). A
main effect of time (p <0.001, F =473.6) was observed and a trend to main effect of treatment (p =0.055, F =4.075, df =25,
η
2
partial =0.149). 3c. Fold change in
SARS-CoV-2 Spike S1-RBD IgG relative to pre-immunization, (90 m exercise >no exercise *p =0.048, F =4.37, df =25,
η
2
partial =0.160; 1wk post dose 2 >2wk
post initial vaccine, p <0.001, F =200.4 df =25). 3d. Fold change in SARS-CoV-2 Spike S1-RBD IgG relative to pre-immunization as compared by exercise, age, and
time post-immunization. Antibody response in middle aged adults <young adults (main effect of age, p =0.003, F =11.3, df =25,
η
2
partial =0.350) and exercise
treatment trended towards a difference based on age (exercise by age ×antibody interaction, p =0.057, F =4.06 df =25).
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
7
3.4. Antibody response to inuenza A/PR/8/34 inactivated vaccine and
effect of exercise duration in mouse model
A rodent model of inuenza immunization was used to examine the
effect of varying durations of exercise on antibody response to the
vaccine. The results showed no effect of exercise on antibody level
measured at two weeks post-immunization, but at four weeks after im-
munization, mice exercising for 90 min had signicantly greater serum
antibody level than no exercise or 180 min of exercise (Fig. 4a and in-
dividual data shown in Supplement Figure S7a). The IgG1 subclass of
antibody was measured at four weeks post-immunization (Fig. 4b), and
results showed a similar pattern to total IgG, although the overall effect
of exercise met the criteria for a statistical trend (p =0.09).
3.5. Requirement for IFN
α
at time of immunization for optimal antibody
response
Separate experiments examined the potential role of IFN
α
as a
mechanism that may contribute to the effects of exercise on antibody
response. Mice treated with anti-IFN
α
antibody or control antibody at
Fig. 4. Mouse Serum anti-Inuenza A/PR/8/34 IgG, IgG1, or IgG2a response to vaccination following varying durations of exercise, and the role of IFN
α
(mice). 4a. Serum
was collected at either 2 weeks or 4 weeks post-immunization (separate mice at 2 weeks and 4 weeks). No signicant effect of exercise at 2 weeks. At 4 weeks of
exercise, exercise treatment altered antibody response (overall signicant effect of exercise, p =0.044, F =3.046, df =34,
η
2
partial =0.233) and post hoc analysis
results indicated serum IgG in mice completing 90 min of exercise >no ex (*p =0.004). 4b. Serum anti-inuenza IgG1 assessed at 4 weeks post-immunization. There
was a statistical trend (overall effect of exercise, p =0.09, F =2.92, df =34,
η
2
partial =0.168) towards a difference between groups. 4c. Total anti-inuenza serum
IgG was measured four-weeks post-immunization. Anti-IFN
α
antibody-treated mice had signicantly less IgG but exercise increased IgG in both anti-IFN
α
treated
mice and mice treated with irrelevant antibody (main effect of antibody, * p <0.001, F =28.3, df =38,
η
2
partial =0.447 ; main effect of exercise, p =0.002, F =
11.5, df =38,
η
2
partial =0.247). There was no signicant exercise group * anti-IFN
α
interaction, p =0.128). 4d & 4e. Anti-inuenza serum IgG1 (6b) or IgG2a (6c)
were measured at four weeks post-immunization. Without IFN
α
, antibody response was signicantly reduced for IgG1 (main effect of IFN
α
antibody treatment, p <
0.001, F =24.5, df =38,
η
2
partial =0.447) and exercise treatment signicantly increased IgG1 (p <0.001, F =23.5, df =38,
η
2
partial =0.402), and there was a
trend towards an anti-IFN
α
antibody by exercise treatment interaction (p =0.06). With respect to IgG2a there was a signicant interaction between exercise
treatment and anti-IFN
α
antibody (exercise * antibody interaction, p =0.014, F =6.63, df =38,
η
2
partial =0.159) implying the exercise effect was not consistent
across antibody treatment. For IgG2a, effect of exercise (p <0.001, F =23.73, df =38,
η
2
partial =0.404) and IFN
α
antibody treatment, p <0.001, F =31.6, df =38,
η
2
partial =0.475). 4f. The signicant interaction for IgG2a (from 4f) is shown in a line graph format.
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
8
the time of immunization completed either 90 min of exercise or no
exercise. The results of serum anti-inuenza IgG antibody, IgG1, and
IgG2a were similar in that a lack of IFN
α
at the time of immunization
signicantly impaired antibody response (Fig. 4c 4f). Mice assigned to
the 90-minute exercise intervention had higher IgG, IgG1, and IgG2a
than no exercise mice, regardless of whether mice received anti-IFN
α
antibody treatment. However, there was a signicant interaction with
respect to IgG2a in which the anti-IFN
α
antibody treatment attenuated
the effect of exercise (signicant exercise by IFN
α
antibody treatment
interaction, Fig. 4e and 4f), suggesting that IFN
α
may contribute to some
extent to the effect of exercise on antibody class switching. Individual
mouse data is shown in Supplement Figures S7b-S7d.
4. Discussion
The ndings presented here demonstrate that 90 min of exercise
after immunization increases antibody response several weeks later
across several immunization models. To the best of our knowledge, these
ndings are the rst to show that light- to moderate-intensity long-
duration exercise enhances antibody response across several vaccine
formulations, including COVID-19 vaccination. These results may have
immediately translatable public health relevance as the exercise para-
digm is straightforward to implement and does not require special
equipment. The exercise intervention is feasible for people who exercise
regularly at light intensities such as walking, and persons with a range of
health characteristics were able to complete the exercise. For example,
nearly half of the participants in the COVID-19 vaccination trial had a
BMI in the overweight or obese category, and the distance covered in 90
min ranged from approximately four miles to over 10 miles, represent-
ing a variety of tness levels as heart rate and relative perceived exertion
level were maintained within a constant range. It will be essential to
determine the length of time post-vaccination for which an exercise-
associated increase in serum antibody may be present. Longer term
antibody response will be assessed as these ndings are an early report.
It would also be helpful to dene how the change in antibody translates
to protection from infection. However, appropriate study designs to
address that question typically require thousands of participants, and
may not be feasible, in which case inference from antibody level and
protection studies will be necessary. Serum antibody is recognized as an
immune correlate of protection for inuenza (Potter and Oxford, 1979),
including IgG measured by ELISA (Trombetta, et al. 2018), and therefore
we expect that the increase in antibody that we report would confer
some benet. The immune correlates of protection from COVID-19
vaccination are under investigation, but early evidence supports
serum antibody as a potential correlate (Sadarangani, et al. 2021).
In comparing the results from our studies with the existing literature
on exercise and vaccines, one limitation that arises is the wide variety of
exercise approaches used. To our knowledge, there are no other studies
that investigated the immunomodulatory effects of a 90-minute aerobic
exercise session. However, of the studies that examined aerobic exercise
rather than eccentric exercise, there were conicting results. For
example, one study showed no benet in antibody response to either
pneumococcal or inuenza vaccine after 45 min of aerobic exercise
(Long, et al. 2012). In other studies, mixed results were found in
response to 45 min of dynamic exercise or aerobic exercise, with an
increase in antibody response to one antigenic component of inuenza
vaccine, but not both inuenza A antigens, and variable results by sex
were present (Edwards, et al. 2006; Ranadive, et al. 2014). Although the
timing of exercise in relation to vaccination was different in our ex-
periments with exercise performed after immunization, we observed
that 45 min of exercise was of insufcient duration to increase antibody
response to either inuenza A antigen (in young or aged adults) or in a
mouse model of inuenza A vaccination. Therefore, our ndings align
with the current literature reporting that aerobic exercise interventions
of 45 min or less do not enhance the antibody response following
inuenza A vaccination.
Notably, there were no differences in the total number of side effects
or duration of side effects in exercise compared to no exercise subjects in
response to the vaccine with greater reactogenicity (COVID-19), indi-
cating a potential benet of exercise with no change in side effect pro-
le. No adverse reactions to either of the inuenza vaccines were
reported. Two separate studies found decreased side effects of exercisers
versus non-exercisers (Bohn-Goldbaum, et al. 2020; Lee, et al. 2018). We
did not see a similar exercise-associated reduction of vaccine side ef-
fects, but exercise mode and duration differed, and COVID-19 vaccine
reactogenicity may also differ, thereby limiting the ability to make
direct comparisons.
The mechanisms by which exercise may increase antibody response
to vaccines remain to be elucidated, although our results provide some
initial support for a potential role of IFN
α
based on ndings from the
mouse model. The exercise-induced enhancement of IgG2a was atten-
uated in mice that received anti-IFN
α
antibody treatment, and a similar
trend was apparent for IgG1. Type I IFN promotes class switching (Le
Bon, et al. 2001), supported by our data showing that mice lacking IFN
α
at the time of immunization had signicantly reduced IgG1 and IgG2a.
IFN
α
also promotes dendritic cell costimulatory molecule expression
and dendritic cell activation (Montoya, et al. 2002; Tough, 2004),
germinal center formation (Le Bon, et al. 2001), and may have direct or
indirect stimulatory effects on B cells and T cells (Le Bon, et al. 2006).
Type I IFN, inducers of Type I IFN, or IFN
α
alone have adjuvant prop-
erties as demonstrated in an inuenza model (Junkins, et al. 2018;
Proietti, et al. 2002), may specically stimulate IgG2c or IgA antibody in
response to inuenza vaccine (Ye, et al. 2019), and may serve as a
mucosal adjuvant in porcine inuenza vaccination (Liu, et al. 2019).
Inducers of IFN
α
(imiquimod) delivered intradermally with inuenza
vaccine improved antibody response in young or older adults (Hung,
et al. 2016; Hung, et al. 2014). Altogether, the evidence from these
studies suggests that IFN
α
can have immunostimulatory effects and
adjuvant activity for vaccines. Therefore, if exercise results in signicant
increases in IFN
α
, or the ability to produce greater IFN
α
upon stimula-
tion, IFN
α
may be one mechanism by which exercise improves antibody
response to vaccines. With 90 min of exercise, we had previously
observed a signicant increase in IFN
α
by human plasmacytoid den-
dritic cells (Table S1). We acknowledge that 90 min of exercise in a
mouse is not directly translatable to humans, but the mouse model af-
fords the opportunity to begin identifying potential mechanisms.
Considering other possible mechanisms, the lack of response to 45
min of aerobic exercise compared with enhanced antibody response to
immunization with 90 min of exercise may provide some insight. Ex-
ercise duration and intensity inuence the metabolic and neuroendo-
crine responses to exercise. Multiple aspects of the vaccine itself,
including the dose of antigen, the inclusion of antigens, the delivery
route, the vaccine platform (lipid nanoparticle encapsulated-mRNA
compared to subunit/split virus preparation), may impact the kinetics
and quality of antigen-presenting cell response and subsequent activa-
tion of T cell and B cell response (Bachmann and Jennings, 2010;
Chappell, et al. 2014; Liang, et al. 2017; Zeng, et al. 2020). These factors
may inuence the immunomodulatory effects of exercise. The ndings
presented here provide initial insights into mechanisms to further
explore in future studies. Our results suggest a possible partial role for
IFN
α
and show that exercise benets extend across different vaccine
formulations but require 90 min of light- to moderate-intensity exercise
instead of only 45 min. Our ndings also cannot rule out or conrm a
role for IL-6 as a potential mechanism by which exercise may contribute
to enhanced antibody response. One might expect a dose response such
that as exercise duration increases, IL-6 increases (Fischer, 2006). The
data presented in the mouse model of vaccination in which 45, 90, and
180 min of exercise were compared do not support a potential dos-
eresponse effect of IL-6, but the experimental design did not specically
address IL-6.
A limitation of the ndings from these experiments is the relatively
small number of participants. However, the reproducibility of the results
J. Hallam et al.
Brain Behavior and Immunity 102 (2022) 1–10
9
across three different human vaccine experiments with varying vaccine
formulations (inactivated, mRNA-based) that contain either novel an-
tigens or antigens to which participants had previous exposure (seasonal
inuenza vaccine) lends credence to these results. Studies in a mouse
model replicated the ndings in human experiments. Although the
conclusions of the COVID-19 vaccination are an early report with rela-
tively limited sample size, analysis of long-term antibody response will
be performed. Due to the potential public health relevance, these early
ndings with COVID-19 were reported. Larger scale trials should be
undertaken that conrm these ndings and examine the extent to which
similar effects may occur after booster immunizations. From a public
health perspective, it would be worthwhile to determine whether an
exercise duration that falls between 45 and 90 min would confer some
benet as more adults may be able to complete an exercise session that is
less than 90 min. Another limitation of the ndings is that the mouse
experiments involved only male mice, and therefore it remains possible
that these ndings may not apply to female mice. The human studies
included males and females but with a limited number of participants, it
was not possible to establish whether there were signicant sex effects.
In future studies, it will be important to establish whether sex by exer-
cise interactions exist and inuence any exercise-associated changes in
the antibody response to vaccine.
In summary, our results are the rst to demonstrate an exercise-
induced enhancement of antibody response to COVID-19 immuniza-
tion without an increase in reported side effects. Our ndings also show
longer-duration light- to moderate-intensity exercise increases antibody
response across different vaccine formulations, and exercise-induced
alterations of IFN
α
may partially contribute to this effect.
Declaration of Competing Interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
the work reported in this paper.
Acknowledgements
This research did not receive any specic grant from funding
agencies in the public, commercial, or not-for-prot sectors.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.bbi.2022.02.005.
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... Despite it, some vaccinated individuals may still experience severe or critical COVID-19 due to a poorer response to immunization. This may result from primary and secondary immune deficiencies, immunosenescence in the elderly, and various lifestyle factors [9][10][11]. ...
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In a cohort of BNT162b2 (Pfizer–BioNTech) mRNA vaccine recipients (n = 1,090), we observed that spike-specific IgG antibody levels and ACE2 antibody binding inhibition responses elicited by a single vaccine dose in individuals with prior SARS-CoV-2 infection (n = 35) were similar to those seen after two doses of vaccine in individuals without prior infection (n = 228). Post-vaccine symptoms were more prominent for those with prior infection after the first dose, but symptomology was similar between groups after the second dose. Virus-specific antibody levels after a single dose of the BNT162b2 vaccine in individuals previously infected with SARS-CoV-2 are similar to levels after two doses of the vaccine in infection-naive individuals.
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