Introduction The association between influenza vaccination and coronavirus disease 2019 (COVID-19) remains controversial. This meta-analysis aimed to investigate whether influenza vaccination reduces the susceptibility and severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Methods A systematic literature search of PubMed, Web of Science, the Cochrane Library, Embase, China National Knowledge Infrastructure, SinoMed, Wanfang Data Knowledge Service Platform, and China Science and Technology Journal VIP Database was conducted from database inception to August 2021. The pooled relative risk (RR) with 95% CI was used to estimate the effect of influenza vaccination on COVID-19. The I2 value was used to assess heterogeneity. If I2 >50%, the random effects model was used as the pooling method. Results Twenty-three published articles with 1,037,445 participants were identified. This meta-analysis showed that influenza vaccination was associated with reduced risk of COVID-19 infection (RR=0.83, 95% CI=0.76, 0.90) and hospitalization (RR=0.71, 95% CI=0.59, 0.84), though not significantly associated with intensive care unit admission and death (risk of intensive care unit admission: RR=0.93, 95% CI=0.64, 1.36; risk of death: RR=0.83, 95% CI=0.68, 1.01). Further analysis suggested that the tetravalent influenza vaccine may be associated with a reduced risk of COVID-19 infection (RR=0.74, 95% CI=0.65, 0.84). Conclusions The results suggest that that influenza vaccination is associated with reduced susceptibility to or disease severity of COVID-19, and influenza vaccination may reduce the risk of COVID-19 and improve clinical outcomes.
- All age groups
- Healthcare workers
- Pregnant women
- Risk factor
- COVID-19
