Abstract
AIMS: Influenza vaccination is associated with reduced cardiopulmonary morbidity and mortality among patients with heart failure or recent myocardial infarction. The immune response to vaccination frequently results in mild adverse reactions (AR), which leads to vaccine hesitancy. This post hoc analysis explored the association between vaccine-related AR and morbidity and mortality in patients with high-risk cardiovascular disease. METHODS AND RESULTS: The INVESTED trial randomized 5260 patients with recent heart failure hospitalization or acute myocardial infarction to high-dose trivalent or standard-dose quadrivalent inactivated influenza vaccine. We examined the association between vaccine-related AR and adverse clinical outcomes across both treatment groups in propensity-adjusted models. Among 5210 participants with available information on post-vaccination symptoms, 1968 participants (37.8%) experienced a vaccine-related AR. Compared to those without AR, post-vaccination AR, most commonly injection site pain (60.3%), were associated with lower risk for the composite of all-cause death or cardiopulmonary hospitalization (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.75-0.92, p < 0.001), cardiopulmonary hospitalizations (HR 0.85 [95% CI 0.76-0.95], p = 0.003), all-cause death (HR 0.77 [95% CI 0.62-0.96], p = 0.02), cardiovascular hospitalizations (HR 0.88 [95% CI 0.78-0.99], p = 0.03) and non-cardiopulmonary hospitalizations (HR 0.80 [95% CI 0.69-0.92], p = 0.003). While mild (76.4%) and moderate (20.6%) AR were most common and together associated with lower risk for the primary outcome (HR 0.81 [95% CI 0.74-0.90], p < 0.001), severe AR (2.9%) were related to increased risk (HR 1.68 [95% CI 1.17-2.42], p = 0.005). CONCLUSION: Mild to moderate post-vaccination reactions after influenza vaccine were associated with reduced risk of cardiopulmonary hospitalizations and all-cause mortality in patients with high-risk cardiovascular disease, while severe reactions may indicate increased risk. Mild to moderate AR to influenza vaccination may be a marker of immune response and should not deter future vaccinations.