Prevention of influenza during mismatched seasons in older adults with an MF59-adjuvanted quadrivalent influenza vaccine: a randomised, controlled, multicentre, phase 3 efficacy study
RCT (n=6,761) found an overall vaccine efficacy for an adjuvanted quadrivalent influenza vaccine of 19.8% against all influenza, in terms of RT-PCR-confirmed influenza cases, owing to a significant degree of isolates (mainly H3N2) mismatched to the vaccine.
Source:
The Lancet Infectious Diseases
SPS commentary:
The efficacy was 49.9% in antigenically matched strains as measured by influenza-like illness.
A related commentary discusses the research, highlighting, amongst other points, that these findings highlight the limitations of widely used approaches to assessing vaccine efficacy by detecting viral shedding by means of RT-PCR endpoints, given that the vaccine reduced the severity of the disease.