INfluenza Vaccine Indication During therapy with Immune checkpoint inhibitors: a multicenter prospective observational study (INVIDIa-2)

Background Until now, no robust data supported the efficacy, safety and recommendation for influenza vaccination in patients with cancer receiving immune checkpoint inhibitors (ICIs).Methods The prospective multicenter observational INfluenza Vaccine Indication During therapy with Immune checkpoint inhibitors (INVIDIa-2) study investigated the clinical effectiveness of influenza vaccination in patients with advanced cancer receiving ICIs, enrolled in 82 Italian centers from October 2019 to January 2020. The primary endpoint was the time-adjusted incidence of influenza-like illness (ILI) until April 30, 2020. Secondary endpoints regarded ILI severity and vaccine safety.Results The study enrolled 1279 patients; 1188 patients were evaluable for the primary endpoint analysis. Of them, 48.9% (581) received influenza vaccination. The overall ILI incidence was 8.2% (98 patients). Vaccinated patients were significantly more frequently elderly (p