Vaccines for preventing influenza in healthy adults

Abstract (PubMed)

This Cochrane review (update of 2014 version) assessed the effects of influenza vaccines in healthy adults aged 16–65 years, including pregnant women. We included 52 clinical trials of over 80,000 people. Inactivated parenteral influenza vaccine reduced influenza (RR 0.59, 95% CI 0.51–0.67; high-certainty evidence) and ILI (RR 0.84, 95% CI 0.75–0.95; moderate-certainty evidence) compared with placebo or no intervention. Vaccines reduced influenza by approximately 2.3 cases per 100 vaccinated people (from 2.9 to 0.6), and ILI by approximately 2 per 100 (from 21.5 to 18.8). Evidence of an effect on hospitalisation was very low certainty. Live aerosol vaccines had similar effects but slightly more local reactions. Vaccine safety profiles were acceptable. The review identified important gaps in evidence on the effects of vaccination in pregnant women, the elderly, and people with chronic conditions. Certainty of evidence rated using GRADE.