High-dose quadrivalent influenza vaccination was associated with lower odds of several cardiovascular and influenza-related hospitalizations in adults aged 65 years or older, according to a meta-analysis of randomized controlled trials published in Immunity & Ageing.

The analysis included four randomized controlled trials involving 511,890 participants aged 65 years or older and compared the high-dose quadrivalent influenza vaccine (HD-QIV) with the standard-dose quadrivalent influenza vaccine (SD-QIV). Trials were identified through searches of PubMed, Cochrane Library, Embase, Web of Science, and Scopus through February 2026. Prespecified subgroup analyses evaluated outcomes according to baseline cardiovascular disease (CVD) status.

HD-QIV was associated with lower odds of cardio-respiratory hospitalization (odds ratio [OR] 0.93; 95% confidence interval [CI] 0.90-0.97) and cardiovascular hospitalization (OR 0.93; 95% CI 0.89-0.98). Lower odds were also observed for hospitalization due to influenza (OR 0.61; 95% CI 0.50-0.74), laboratory-confirmed influenza hospitalization (OR 0.69; 95% CI 0.56-0.86), and heart failure (HF) hospitalization (OR 0.80; 95% CI 0.69-0.94).

No significant differences were identified for respiratory hospitalization, all-cause hospitalization, all-cause mortality, myocardial infarction (MI), or serious adverse events. Subgroup analyses showed no significant differences according to baseline CVD status.

The findings showed that HD-QIV was associated with modest reductions in cardiovascular and influenza-related hospitalizations in older adults, while serious adverse event rates were similar between HD-QIV and SD-QIV.