Association between influenza vaccination and reduced risks of major adverse cardiovascular events in elderly patients.

BACKGROUND: This study was conducted to determine the protective effect of influenza vaccine against primary major adverse cardiovascular events (MACEs) in elderly patients, especially those with influenza-like illness (ILI).

METHODS: This retrospective, population-based case-control study of an elderly population (age≥65 years) was conducted using Taiwan's National Health Insurance Research Database (2000-2013). One control was selected for each MACE case (n=80,363 each), matched according to age, year of study entry, and predisposing factors for MACEs. ILI and MACEs (myocardial infarction [MI] and ischemic stroke) were defined according to the International Classification of Diseases, Ninth Revision, Clinical Modification. Odds ratios (ORs) were calculated for the association between MACEs and vaccination.

RESULTS: Influenza vaccination received in the previous year was associated with reduced risks of primary MACEs overall (adjusted OR [aOR] 0.80, 95% CI 0.78-0.82, P<.001), MI (aOR 0.80, 95% CI 0.76-0.84, P<.001), and ischemic stroke (aOR 0.80, 95% CI 0.77-0.82, P<.001). ILI diagnosed in the previous year was associated with increased risks of MACEs (aOR 1.24, 95% CI 1.18-1.29, P<.001), MI (aOR 1.46, 95% CI 1.34-1.59, P<.001), and ischemic stroke (aOR 1.16, 95% CI 1.10-1.22, P<.001). Vaccination attenuated the heightened risks associated with ILI (MACEs: aOR 0.99, 95% CI 0.92-1.07, P=.834; MI: aOR 1.05, 95% CI 0.92-1.21, P=.440; ischemic stroke: aOR 0.96, 95% CI 0.89-1.05, P=.398).

CONCLUSIONS: Results of this study suggest that influenza vaccination is associated with reduced primary MACE risks in the elderly population, including those with ILI.