AS03-adjuvanted versus non-adjuvanted inactivated trivalent influenza vaccine against seasonal influenza in elderly people: a phase 3 randomised trial

Background We aimed to compare AS03-adjuvanted inactivated trivalent influenza vaccine (TIV) with non-adjuvanted TIV for seasonal influenza prevention in elderly people. Methods We did a randomised trial in 15 countries worldwide during the 2008-09 (year 1) and 2009-10 (year 2) influenza seasons. Eligible participants aged at least 65 years who were not in hospital or bedridden and were without acute illness were randomly assigned (1:1) to receive either AS03-adjuvanted TIV or non-adjuvanted TIV. Randomisation was done in an interne-based system, with a blocldng scheme and stratification by age (65-74 years and 75 years or older). Participants were scheduled to Findings We enrolled 43802 participants, of whom 21893 were assigned to and received the AS03-adjuvanted TIV and 21802 the non-adjuvanted TIV in year 1. In the year 1 efficacy cohort, fewer participants given AS03-adjuvanted than non-adjuvanted TIV were infected with influenza A or B, or both (274 [1.27%, 95% CI 1.12-1.43] of 21573 vs 310 [1.44%, 1.29-1.61] of 21482; relative efficacy 12-11%, 95% CI -3.40 to 25.29; superiority not established). Fewer participants in the year 1 efficacy cohort gi Interpretation AS03-adjuvanted TIV has a higher efficacy for prevention of some subtypes of influenza than does a non-adjuvanted TIV. Future influenza vaccine studies in elderly people should be based on subtype or lineage-specific endpoints.