RESUMEN
BACKGROUND: Influenza vaccination prevents major cardiovascular events in individuals presenting a recent acute coronary syndrome (ACS), however the early effect of an in-hospital double-dose vaccination strategy remains uncertain. METHODS: The VIP-ACS was a randomized, pragmatic, multicenter, open-label trial with a blinded-adjudication endpoint. Patients with ACS ≤ 7 days of hospitalization were randomized to an in-hospital double-dose quadrivalent inactivated influenza vaccine (double-dose) or a standard-dose influenza vaccine at 30 days post-randomization. The primary endpoint was a hierarchical composite of death, myocardial infarction, stroke, hospitalization for unstable angina, hospitalization for heart failure, urgent coronary revascularization, and hospitalization for respiratory infections, analyzed with the win ratio (WR) method in short-term follow-up (45-days after randomization). RESULTS: The trial enrolled 1,801 patients (≥18 years old). Median participant age was 57 years, 70 % were male. There were no significant differences between groups on the primary hierarchical endpoint: there were 5.7 % wins in the double-dose in-hospital group and 5.5 % wins in the standard-dose delayed vaccination group (WR: 1.03; 95 % CI: 0.70---1.53; P = 0.85). In a sensitivity analysis including COVID-19 infection in the hospitalizations for respiratory infections endpoint, overall results were maintained (WR: 1.03; 95 % CI 0.71---1.51; P = 0.87). Results were consistent for major cardiovascular events only (WR: 0.82; 95 % CI: 0.48---1.39; P = 0.46). No serious adverse events were observed. CONCLUSION: In patients with recent ACS, in-hospital double-dose influenza vaccination did not significantly reduce cardiorespiratory events at 45 days compared with standard-dose vaccination at 30 days post-randomization.