---
title: "Physical activity, fitness, and antibody responses to influenza vaccination in adults: systematic"
id: "frontiers-in-immunology-12-exercise-physical-activity-physical-fitness-and-humoral-responses-to-influenza"
canonical_url: "https://medichelpline.com/clinical-feed/frontiers-in-immunology-12-exercise-physical-activity-physical-fitness-and-humoral-responses-to-influenza"
content_type: "clinical_feed_article"
specialty: "Infectious Disease"
source_name: "Frontiers in Immunology"
source_url: "https://www.frontiersin.org/articles/10.3389/fimmu.2026.1950491"
published_at: "2026-10-08T00:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Physical activity, fitness, and antibody responses to influenza vaccination in adults: systematic
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/frontiers-in-immunology-12-exercise-physical-activity-physical-fitness-and-humoral-responses-to-influenza
- **Specialty:** [Infectious Disease](https://medichelpline.com/clinical-feed/infectious-disease.md)
- **Primary Source:** Frontiers in Immunology
- **Source URL:** [Original Journal Publication](https://www.frontiersin.org/articles/10.3389/fimmu.2026.1950491)
- **Published At:** 2026-10-08T00:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- The source article's metadata indicates a systematic review on the relationship between **exercise, physical activity, physical fitness** and **humoral responses to influenza vaccination** in adults, published in Frontiers in Immunology. - The provided SOURCE JINA BODY contains only website and journal navigation elements; the article text, methods, results, and conclusions were not included. - Key study details — including search strategy, inclusion criteria, number and characteristics of included studies, effect estimates, statistical methods, and risk-of-bias assessments — are not reported in the source text available here. - No quantitative findings, subgroup analyses, or pooled effect sizes for antibody titers, seroconversion, or seroprotection following influenza vaccination are present in the provided content. - There are no reported participant demographics (age ranges, health status, baseline fitness or activity levels), intervention definitions (type, intensity, duration of exercise), or timing relative to vaccination. - The source provides no details on heterogeneity, sensitivity analyses, publication bias, or certainty of evidence (e.g., GRADE). - Because the article content is missing from the supplied source, definitive clinical implications or recommendations about the impact of **exercise** or **physical activity** on influenza vaccine humoral responses cannot be extracted or summarised from this input. - Further reading should consult the full article on the publisher site for precise methods, results, and authors' conclusions before applying to practice or research planning.
## Clinical Analysis & Structured Key Points
Frontiers | Exercise, physical activity, physical fitness, and humoral responses to influenza vaccination in adults: a systematic review and meta-analysis SYSTEMATIC REVIEW article Front. Immunol. , 08 October 2026 Sec. Vaccines and Molecular Therapeutics Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1950491 Published in Frontiers in Immunology Vaccines and Molecular Therapeutics 7 impact factor 11.3 citescore Editor & Reviewers Edited by J M Jochen Mattner Reviewed by S R Sahar Rahimi C N Chiara Noviello Outline Figures and Tables Figure 1 View in article Figure 2 View in article Figure 3 View in article Figure 4 View in article Figure 5 View in article Table 1 Characteristics of the included reports. View in article Table 2 Detailed exercise/exposure characteristics of the included studies. View in article Table 3 Primary randomized estimates, separated by acute exercise and chronic training. View in article Table 4 Overall risk of bias for humoral results in the included reports. View in article Table 5 Summary of findings (GRADE) for the primary randomized comparisons. View in article SYSTEMATIC REVIEW article Front. Immunol. , 08 October 2026 Sec. Vaccines and Molecular Therapeutics Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1950491 Exercise, physical activity, physical fitness, and humoral responses to influenza vaccination in adults: a systematic review and meta-analysis X H Xiaoman Hao 1 † T Y Tianyuan Yu 2 † W L Weibao Liang 3 † Y Z Yue Zong 4 Y Z Yasong Zhang 5 Y H Yu Hou 6 Z S Zhijia Sun 7 * 1. School of Physical Education, Chengdu Vocational University of the Arts, Chengdu, China 2. School of Information Technology, Vitebsk State University named after P.M. Masherov, Vitebsk, Belarus 3. South China Normal University, Guangzhou, China 4. School of Physical Education, Guangdong Technology College, Zhaoqing, China 5. Department of Basic Medicine, Langfang Health Vocational College, Langfang, China 6. College of Sports Science, Shenyang Normal University, Shenyang, China 7. Hebei Sport University, Shijiazhuang, China See more Article metrics View details Abstract Background: Exercise, habitual physical activity, and physical fitness have been proposed as behavioral adjuvants that could improve influenza vaccine immunogenicity, but individual studies are small and inconsistent. Objective: To evaluate the effects of assigned acute and chronic exercise interventions, and the associations of habitual activity and fitness, with humoral responses to influenza vaccination in adults. Methods: We searched PubMed, Web of Science, Embase, Cochrane Library, Scopus, and SPORTDiscus from inception to May 1, 2026. Randomized evidence was analyzed separately for acute exercise and chronic training; nonrandomized interventions and observed activity or fitness were considered separately. Risk ratios (RRs) and mean differences (MDs) in log 2 hemagglutination inhibition (HAI) titers were synthesized when compatible numerical data were available. Design-appropriate risk-of-bias tools and GRADE were applied. Results: Twenty-two reports were included. Seven randomized reports provided primary quantitative estimates, and five contributed to at least one meta-analysis of two or more trials. Acute exercise did not show a clear effect on H1N1 seroprotection (RR 0.88, 95% CI 0.65–1.21; k = 3) or H3N2 seroprotection (RR 1.04, 0.91–1.20; k = 3), or on H1N1 seroconversion (RR 1.30, 0.58–2.92; k = 2) or H3N2 seroconversion (RR 0.84, 0.50–1.40; k = 2). Chronic-training titer estimates were imprecise for H1N1 (MD 0.50 log 2 units, −0.64 to 1.64; k = 2), H3N2 (0.27, −0.17 to 0.72; k = 2), and influenza B (−0.14, −0.64 to 0.36; k = 2). Other primary comparisons were supported by single trials. Certainty was low or very low. Conclusion: The available randomized evidence does not establish an immunogenicity benefit of acute exercise or chronic training, but does not demonstrate equivalence or exclude benefit. Observational associations remain vulnerable to confounding. Larger trials with complete numerical reporting are needed; these antibody findings do not establish effects on clinical influenza. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261425732 , identifier CRD420261425732. Introduction Seasonal influenza causes a substantial and recurrent global burden of illness. Modeling studies estimate that influenza-associated respiratory deaths number in the hundreds of thousands each year, with the highest mortality rates in adults aged 75 years and older, and the Global Burden of Disease analyses attribute tens of millions of episodes of lower respiratory tract infection to influenza annually ( 1 , 2 ). Annual vaccination remains the principal preventive strategy, but its effectiveness is only moderate and varies markedly by season, by circulating strain and by the age and health of the recipient ( 3 ). A large part of that variability is immunological. Antibody responses to inactivated influenza vaccine decline with age: a quantitative review of trials in older adults found consistently lower seroconversion and seroprotection rates than in younger recipients ( 4 ). The underlying changes, collectively described as immunosenescence, include thymic involution, contraction of the naive T-cell repertoire, impaired germinal-center and B-cell function and a chronic low-grade inflammatory state ( 5 – 7 ). These changes translate directly into weaker vaccine-induced humoral immunity, and they are one reason why strategies to improve vaccine responses in older adults are a persistent public-health priority ( 8 – 10 ). Serum hemagglutination inhibition (HAI) antibody remains the most widely used immunological read-out in this field: a post-vaccination titer of at least 1:40 has been associated with roughly a 50% reduction in the risk of infection in the classical challenge studies, and later analyses have refined, without displacing, that relationship ( 11 – 13 ). Not all of the variation in vaccine response is fixed. Host and behavioral factors, including nutritional status, psychological stress, sleep, and physical activity, may influence the immune response to vaccination ( 14 ). Chronic psychological stress is associated with poorer antibody responses to influenza vaccine ( 15 – 17 ). Evidence that sleep after hepatitis A vaccination supports immunological memory provides broader vaccine-related context rather than direct evidence about influenza vaccination ( 18 ). Interest in behavioral adjuvants follows naturally: interventions delivered near vaccination could potentially improve immunogenicity without reformulating the vaccine. Exercise is the most extensively studied candidate. The view that exercise suppresses immunity has been substantially revised; contemporary syntheses argue that acute exercise transiently redeploys immune cells rather than depleting them, and that regular physical activity is associated with better immune competence across the lifespan ( 19 – 21 ). Habitual physical activity and higher cardiorespiratory fitness are associated with attenuated features of immunosenescence, including greater thymic output and a more favorable T-cell phenotype ( 22 – 25 ). Two broad mechanistic rationales have been proposed for a vaccine-specific effect. Acute exercise performed close to immunization may act as an adjuvant by increasing local blood and lymph flow, enhancing antigen delivery to draining lymph nodes, and by generating a transient neuroendocrine and inflammatory milieu, mediated in part by catecholamines and by muscle-derived interleukin-6, that favors antigen presentation and lymphocyte trafficking ( 26 – 29 ). Long-term training and habitual activity may instead act by improving the baseline immune environment, including a reduction in chronic low-grade inflammation ( 30 , 31 ). Physical activity is already recommended for adults of all ages on other grounds, so any additional benefit for vaccine responses would strengthen an existing public-health message rather than create a new one ( 32 – 34 ). The empirical picture is, however, unsettled. Individual studies examine exposures ranging from a single exercise bout near vaccination to months of training or pre-existing activity and fitness, and use different antibody metrics and follow-up schedules. An individual-participant-data meta-analysis has already examined acute exercise and habitual activity in relation to influenza vaccine responses, while a broader meta-analysis has examined exercise and vaccination across vaccine types ( 35 , 36 ). A systematic review of physical activity and immune function also included vaccination outcomes, and a Cochrane review specifically evaluated exercise before influenza vaccination ( 37 , 38 ). The contribution of the present review is therefore not the first synthesis of this question, but a design- and exposure-specific reassessment of strain-specific humoral outcomes, numerical extractability, risk of bias, and certainty. We therefore asked whether assigned acute exercise or chronic exercise training changes humoral responses to influenza vaccination in adults, and whether observed habitual activity or fitness is associated with those responses. Acute exercise, chronic training, observed activity or fitness, and exercise-based mind-body interventions were distinguished rather than treated as interchangeable exposures. Older adults were identified as a subgroup of interest. Methods Protocol, registration and reporting The review protocol was registered in PROSPERO (CRD420261425732). Reporting follows the PRISMA 2020 statement and the PRISMA-S search-reporting extension ( 39 , 40 ). Data handling and synthesis were informed by the Cochrane Handbook for Systematic Reviews of Interventions ( 41 ). During revision, the analyses were separated by exposure duration and study design, ambiguous source values were removed from primary estimates, and the certainty assessments were reconsidered. These revisions and the additional sensitivity analyses are reported as amendments, not as prespecified analyses. Eligibility criteria Studies were eligible if they enrolled adults aged 18 years or older who received influenza vaccination. Eligible exposures were acute exercise, long-term exercise training, habitual physical activity, physical fitness, and Taiji, Qigong or other exercise-based interventions in which the exercise contrast could be separated from co-interventions. Eligible comparators were rest or no exercise, lower activity or lower fitness, non-trained participants, waitlist or usual lifestyle, or an eligible active control condition. Continuous exposure-antibody associations were eligible, and studies reporting three or more ordered exposure levels were retained for exposure-gradient analysis. Primary humoral outcomes were HAI antibody titers, geometric mean titers (GMTs), fold rise, seroprotection (postvaccination HAI titer ≥1:40), and seroconversion (a ≥4-fold rise). Secondary humoral outcomes included influenza-specific IgG, IgM, IgA, and neutralizing antibody. Cell-mediated immunity and vaccine reactions were supplementary outcomes and did not substitute for a humoral outcome when determining review eligibility. Randomized trials, nonrandomized exercise interventions, and observational exposure studies with an eligible comparison were considered. We excluded non-adult samples without separable adult results, vaccines other than influenza vaccine, multicomponent interventions without an identifiable exercise contrast, studies without an eligible exposure comparison or humoral response, animal studies, reviews, and duplicate outcome reports. Availability of compatible numerical data determined inclusion in a quantitative synthesis rather than automatically determining eligibility for narrative review. Reports from overlapping cohorts were linked, and a cohort was not entered twice in the same synthesis. Report counts and participant counts were distinguished; a sum across overlapping reports was not interpreted as the number of unique participants. Information sources and search strategy Six electronic databases were searched from inception to May 1, 2026: PubMed (MEDLINE), Web of Science Core Collection, Embase, the Cochrane Library (CENTRAL), Scopus, and SPORTDiscus (EBSCOhost). Each strategy combined exercise/activity/fitness, influenza vaccination, and humoral immune-response concepts. No language or date restrictions were applied at the search stage. The full database-specific strategies are reproduced in Supplementary Table S1 . The search was restricted to these bibliographic databases; trial registries and gray-literature sources were not searched. The humoral-outcome block may have reduced sensitivity when eligible outcomes were not described in searchable fields, and using several databases does not remove that shared restriction. Supplementary Table S2 provides the numerical estimates and analysis status, Supplementary Table S3 supports the design-specific risk-of-bias judgments, Supplementary Table S4 reports sensitivity analyses, Supplementary Table S5 describes nonpooled findings and observational associations, and Supplementary Table S6 provides the GRADE evidence profiles. Supplementary Table S7 documents numerical provenance, reconstruction methods, and exclusions, including the exclusion of exploratory figure-derived readings from Hallam et al. Study selection and data collection Records were managed and deduplicated in Zotero 9.0. Two reviewers (Xiaoman Hao and Weibao Liang) independently screened titles and abstracts and assessed potentially eligible full texts against the eligibility criteria. The same reviewers independently extracted data and assessed risk of bias. Disagreements were resolved through discussion and, when necessary, adjudication by a third reviewer (Zhijia Sun). Reasons for exclusion were recorded at the full-text stage. Data were extracted into a structured form covering study design, participants, exercise or activity exposure, comparator, vaccine, humoral outcome, assessment time, and numerical results. Numerical inputs were checked against source tables, text, and printed figure labels. Printed values were distinguished from statistical reconstructions and readings of plotted coordinates. Exploratory digitization of Hallam et al.’s ELISA fold-change figures was not retained in any revised quantitative analysis because overlapping markers and repeated measurements prevented reliable reconstruction of an independent arm-level estimate. Studies without a compatible numerical estimate were summarized narratively; numerical provenance and exclusions are detailed in Supplementary Table S7 . Original investigators were not contacted for missing numerical data. Given the age of several foundational trials and uncertainty about the availability of archived datasets, retrieval of additional numerical information was limited to published reports and their Supplementary Materials . No unpublished investigator-supplied values were used. Unresolved numerical ambiguities were excluded from primary analyses or examined only as explicitly labeled sensitivity scenarios; the absence of author contact may have limited the completeness of the quantitative evidence. Outcome constructs and harmonization Humoral outcomes were distinguished by assay and response construct. HAI titers, HAI fold rise, binary thresholds, and ELISA optical-density measures were not treated as interchangeable. H1N1, H3N2, and influenza B were analyzed separately. For the generic influenza B comparisons, a report had to provide one unambiguous B-antigen result; the two B antigens of quadrivalent-vaccine studies were instead reported separately, without selecting one into the generic B synthesis or counting the same participants twice. Peak responses at approximately 3–6 weeks were considered separately from later follow-up. Postvaccination HAI titers were expressed on a log 2 scale, so an MD of 1 represents one doubling and 2 MD is the corresponding GMT ratio. Kohut (2004) and Woods (2009) provided log 2 means and standard errors directly. For Lee (2021), log 2 (GMT) was used as the arm mean, and the standard error was approximated from the width of the log 2 -transformed 95% confidence limits divided by 2 × 1.96; the arm standard deviation was obtained by multiplying by the square root of the sample size. The same reconstruction was used for the separately reported nonrandomized Edwards (2010) estimates. The logarithm base in Bohn-Goldbaum (2020) was unstated, so its continuous values were excluded from the primary log 2 analysis. H3N2 and influenza B were considered only in assumed-log10 sensitivities. H1N1 was excluded from all continuous analyses because the printed control SD of 0.0653 also raised an unresolved decimal-place ambiguity; no replacement SD was assumed. Binary denominators inferred from rounded percentages were identified as reconstructions. For Lee (2021) fold rise, the published combined-exercise arithmetic mean was compared with control, with standard errors approximated from the printed 95% confidence-limit widths divided by 2 × 1.96. The two B antigens were retained separately. Because its Results text reported B/Brisbane means and SDs that were inconsistent with its fold-rise table, a separate sensitivity used the text-reported values. Rounded or asymmetric confidence limits and discordant dispersion measures limit the precision of these reconstructed single-trial estimates. Where a trial contributed multiple eligible exercise arms against a shared control, exercise arms were combined before estimation. Means and standard deviations were combined using the standard formula including between-arm mean differences; binary event counts and denominators were summed ( 41 ). The shared control was counted once. This applied to the two exercise arms in Elzayat (2021) and Lee (2021), and to the three exercise-intensity arms in the separately reported Edwards (2010) comparison. Risk-of-bias assessment Risk of bias was assessed for humoral results using RoB 2 (2019) for randomized trials, ROBINS-I (2016) for nonrandomized exercise interventions, and ROBINS-E (2024) for observed pre-existing activity or fitness exposures followed by vaccination-response assessment ( 42 – 44 ). Campbell (2010) and Edwards (2010) were described as pseudo-randomized without a demonstrably random sequence and were therefore treated conservatively as nonrandomized; Yang (2007) included additional nonrandomly recruited controls. Kohut (2004) explicitly reported random assignment and was retained as randomized. In Monteiro (2020), supplement randomization did not randomize exercise status; the eligible placebo-arm exercise comparison was treated as observational. Domain meanings and judgment categories were retained separately for each tool. Supplementary Table S3 reports the least favorable humoral-result judgment for each report and explains the relevant allocation, confounding, missing-data, measurement, and reporting concerns. Small sample size, an active comparator, or figure-only reporting was not itself treated as a risk-of-bias domain. Effect measures and synthesis Binary outcomes were expressed as RRs and continuous HAI titers as MDs on the log 2 scale. Raw HAI fold-rise MDs were reported only for compatible, unambiguous numerical results; they were not combined with log-fold measures or ELISA optical-density fold change. Positive MDs or RRs above 1 indicate a stronger humoral response in the exercise condition, not necessarily better clinical protection. Primary syntheses were restricted to randomized exercise comparisons and were conducted separately for acute exercise and chronic training. Pre-existing activity or fitness and nonrandomized interventions were not added to these pools; a single eligible trial was reported as a single-trial estimate. Binary random-effects syntheses used
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