Thought this from Public Health England was of interest
The new adjuvanted flu vaccine given to people aged over 65 years in England for the first time in winter 2018 had a success rate of more than 60% in protecting them against the virus, according to statistics from Public Health England (PHE).
The overall success rate of the vaccine programme against all flu strains for all age groups during the 2018–2019 flu season was 44.3%, according to the annual flu report, which was published on 30 May 2019. In the previous flu season, the overall figure was 15.0%.
The effect of the Live Attenuated Influenza Vaccine given to children and young people aged 2–17 years was 48.6% in the 2018–2019 season.
In the 18–64 years age group, flu vaccination, for all vaccines, was effective in 44.2% of cases; the success rate, for all vaccines, in those aged over 65 years was 49.9%.
However, the success rate shot up to 62.0% in people aged over 65 years who were only given the new adjuvanted flu vaccine, which is designed to be effective against three flu strains.