ReviewVaccines2021
The Association between Influenza Vaccination and COVID-19 and Its Outcomes: A Systematic Review and Meta-Analysis of Observational Studies.
Review in Vaccines, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 48 papers, 3 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
48 citing papers in PubMed, 3 syntheses or guidelines pooled it, 74 citations in OpenAlex.
- Association between influenza vaccination and SARS-CoV-2 infection and its outcomes: systematic review and meta-analysis.Chinese medical journal · 2022Pooled it
- The effect of influenza vaccine in reducing the severity of clinical outcomes in patients with COVID-19: a systematic review and meta-analysis.Scientific reports · 2022Pooled it
- The Association Between Previous Influenza Vaccination and COVID-19 Infection Risk and Severity: A Systematic Review and Meta-analysis.American journal of preventive medicine · 2022Pooled it
- Immunogenicity and safety of concomitant administration of recombinant COVID-19 vaccine and quadrivalent inactivated influenza vaccine in Chinese adults: An open-label, randomized, controlled trial.Human vaccines & immunotherapeutics · 2024Trial
- Trial
- Association between COVID-19 booster vaccination and influenza mortality: a nationwide retrospective cohort study using the SIVEP-Gripe database in Brazil.Immunologic research · 2026Article
- Impact of non-pharmaceutical interventions of the COVID-19 pandemic on the trend of seasonal influenza in Kingdom of Saudi Arabia.BMC infectious diseases · 2025Observational
- Biometric Strategies to Improve Vaccine Immunogenicity and Effectiveness.Biomimetics (Basel, Switzerland) · 2025Review
- Quantifying and Adjusting for Confounding From Health-Seeking Behavior and Health Care Access in Observational Research.Open forum infectious diseases · 2024Article
- Article
- Article
- Article
- Flu vaccine administration in the period before SARS-CoV-2 infection and its outcomes: An umbrella review.Preventive medicine reports · 2024Review
- Influenza and COVID-19 co-infection and vaccine effectiveness against severe cases: a mathematical modeling study.Frontiers in cellular and infection microbiology · 2024Article
- Seroprevalence of SARS-CoV-2 antibodies among healthcare workers in Dutch hospitals after the 2020 first wave: a multicentre cross-sectional study with prospective follow-up.Antimicrobial resistance and infection control · 2023Article
- Opinions, Attitudes and Factors Related to SARS-CoV-2 Vaccine Uptake in Eight South American Countries.Vaccines · 2023Article
- Experimental Infection of Pigs with a Traditional or a Variant Porcine Respiratory Coronavirus (PRCV) Strain and Impact on Subsequent Influenza A Infection.Pathogens (Basel, Switzerland) · 2023Article
- Preschool-located influenza vaccination and influenza-like illness surveillance: an Italian pilot experience.Italian journal of pediatrics · 2023Article
- Lower frequency of SARS-CoV-2-associated severe respiratory infections among adults vaccinated against the 2021/22 season influenza.Respiratory medicine and research · 2023Article
- Impact of COVID-19 Outbreak on Influenza and Pneumococcal Vaccination Uptake: A Multi-Center Retrospective Study.Vaccines · 2023Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
3 authors at 1 institution in 1 country.
Funding
Abstract
Influenza could circulate in parallel with COVID-19. In the context of COVID-19, some studies observed inverse associations between influenza vaccination and SARS-CoV-2 infection and clinical outcomes, while others did not. We conducted a meta-analysis to assess the association between influenza vaccination and SARS-CoV-2 infection and clinical outcomes, aiming to provide evidence for COVID-19 prevention and vaccination promotion. We searched four databases from inception to 10 March, 2021. Random effects and fixed effects models were used to pool odds ratios (ORs) and adjusted estimates with 95% confidence intervals (CIs). We used funnel plots to evaluate the publication bias, I2 statistics to evaluate the heterogeneity, and conducted subgroup analyses. Sixteen observational studies involving 290,327 participants were included. Influenza vaccination was associated with a lower risk of SARS-CoV-2 infection (pooled adjusted OR: 0.86, 95%CI: 0.81-0.91), while not significantly associated with adverse outcomes (intensive care: adjusted OR 0.63, 95%CI: 0.22-1.81; hospitalization: adjusted OR 0.74, 95%CI: 0.51-1.06; mortality: adjusted OR 0.89, 95%CI: 0.73-1.09). Our findings suggest that influenza vaccination is associated with a lower risk of SARS-CoV-2 infection. It is crucial for policy makers to implement strategies on influenza vaccination, for it may also have benefits for COVID-19 prevention.
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What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.