15 Nov 2021
Results from the first UK real world study by the UK Health Security Agency (UKHSA) show significantly increased protection against symptomatic disease from a booster dose of the Pfizer-BioNTech vaccine in those aged 50 years and older.
These findings show that two weeks after receiving a booster dose, protection against symptomatic infection in adults aged 50 years and over was 93.1% in those with AstraZeneca as their primary course and 94.0% for Pfizer-BioNTech.
After a primary course of AstraZeneca and Pfizer-BioNTech vaccines, effectiveness against symptomatic disease appears to wear off with time. Overall, vaccine effectiveness against severe outcomes such as hospital admission remains high for several months after completing the primary course, but greater waning has been seen in older adults and those with underlying medical conditions compared to young, healthy adults. As a result, the JCVI recommended a booster vaccine programme to eligible groups including adults aged 50 years and above on 14 September 2021 and extended this to adults over 40 on 15 November 2021.
Dr Mary Ramsay, Head of Immunisation at the UK Health Security Agency, said: “Our findings demonstrate the protection provided by the booster dose against symptomatic infection in those at highest risk from developing severe COVID-19. We know that in older age groups, protection from the first two vaccines is beginning to wear off, leaving millions that need extra protection as we head into winter. That is why it is critical that you come forward for your booster as soon as you become eligible so we can drive down hospitalisations and deaths over the winter.”
At this early stage of the booster roll-out, due to the natural lag between acquiring infection and suffering from complications this study is only able to assess protection against symptomatic disease. It is expected that, as with the first and second doses, protection against hospitalisation and death will be even higher and help to break the link between infections and severe outcomes.
The analysis shows that, in those who received the booster, the risk of catching symptomatic COVID-19 was reduced by more than an additional 80% compared to those who had only received two doses (87.4% for those who received two doses of AstraZeneca vaccines as a primary course and 84.4% for those who received two doses of Pfizer-BioNTech vaccines as a primary course).