Association between influenza vaccination and one‐year all‐cause and cardiovascular mortality risk: A self‐controlled case series and matched case‐control study

Debates surrounding the efficacy of influenza vaccination for survival benefits persist, and there is a lack of data regarding its duration of protection. A self‐controlled case series (SCCS) and a 1:4 matched case‐control study were conducted using the National Health Interview Survey (NHIS) and public‐use mortality data from 2005 to 2018 in the United States. The SCCS study identified participants who received influenza vaccination within 12 months before the survey and subsequently died within 1 year of postvaccination. The matched case‐control study paired participants who died during the influenza season at the time of survey with four survivors. Among 1167 participants in the SCCS study, there was a 46% reduction in all‐cause mortality and a 43% reduction in cardiovascular mortality within 29–196 days of postvaccination. The greatest protection was observed during days 29–56 (all‐cause mortality: RI: 0.19; 95% CI: 0.12–0.29; cardiovascular mortality: RI: 0.28; 95% CI: 0.14–0.56). Among 626 cases and 2504 controls included in the matched case‐control study, influenza vaccination was associated with a reduction in all‐cause mortality (OR: 0.74, 95% CI: 0.60–0.92) and cardiovascular mortality (OR: 0.64, 95% CI: 0.44–0.93) during the influenza season. This study highlights the importance of influenza vaccination in reducing the risks of all‐cause and cardiovascular mortality, with effects lasting for approximately 6 months.