Acceptance and safety of the intradermal influenza vaccine among the elderly in Italy: an on-field national study.

An observational multicenter study was carried out in Italy, to evaluate the acceptability and safety of the new intradermal (ID) influenza vaccine (Intanza Sanofi Pasteur SA, Lyon, France) among subjects aged≥60 years, compared with that of other intramuscular (IM) influenza vaccines. Compliance with the use of the ID vaccine by healthcare professionals was also assessed.A previously validated and self-administered questionnaire, Vaccinees' Perception of Injection (VAPI®), consisting of 21 questions, mainly focused on four dimensions (bother, arm movements, sleep, and acceptability), was administered to >1,600 individuals with spontaneous access to outpatient clinics, located in Northern, Central, and Southern Italy, to evaluate the acceptance of the vaccines. Occurrence of solicited and unsolicited side effects and of serious adverse events was assessed in a subset of subjects (n=500), using a clinical diary filled in by vaccinees following immunization. Compliance with the new ID vaccine by healthcare professionals was investigated using an ad-hoc questionnaire.A very favorable opinion concerning the acceptability of both the vaccines under survey, with the most positive answers ranging between 75.5\% and 94.9\%, was registered within the study population. Also the compliance by healthcare professionals (n=130) with the novel ID vaccine was favorable. No serious adverse event occurred during the 6-month follow-up period. The frequency of solicited systemic reactions was comparable between the two study groups, while solicited local reactions were significantly higher in the ID-vaccine group than in the IM-vaccine group, even if at values lower than those reported in phase 3 clinical trials (ranges=18.5-32.6\% vs. 29.5-70.9\%). These local events were mild and transient, thus without any clinical relevance.The novel ID influenza vaccine can be widely recommended in clinical practice, representing a useful tool to improve immunization coverage rates, and thus the control of influenza.