There is a continued need for Covid boosters, according to a government study which found they provide significant protection against death but this wanes after six months.
Researchers from the UK Health Security Agency analysed data on more than 10.6 million cases of Covid-19 in adults that had been recorded by England’s laboratory reporting system between May 2020 and February 2022.
They found a clear time link between a fall in ‘case fatality risk’ and when the age group became eligible for Covid-19 vaccination and first booster.
Reporting in the Journal of the Royal Society of Medicine, they also pinpointed that the case fatality risk was also at its lowest for all groups in the six months after vaccination when the protective effect diminished at it began to rise again.
In adults over the age of 50, the case fatality risk was 10 times higher in the unvaccinated (6.3%) compared to those who had been vaccinated in the six months before they tested positive (0.6%), they reported.
The researchers also found a steep decline in mortality from Covid-19 in early 2021, which aligned with the initial vaccine rollout.
They were able to do the detailed analysis because of the wide availability of SARS-CoV-2 testing during the study period, the researchers noted.
Risk of death was also linked to sex, deprivation and ethnicity, they said. But it also fluctuated over time which could relate to the emergence of different variants as well as population immunity from natural exposure to the virus.
But after vaccination was introduced, the case fatality rate remained low in those who took up the offer, they added.
Mortality remained high in the small unvaccinated group even through the changing transmission rates and severity associated with emerging variants indicating that vaccination is a key factor in reducing deaths from Covid-19.
While the study shows that continued booster programmes are needed to keep deaths from Covid-19 low, more investigation is needed on the appropriate age cut offs, the team said.
An analysis from the Joint Committee on Vaccination and Immunisation (JCVI) published in October had noted that it would be most ‘cost-effective’ to limit vaccination to the over 80s and high risk over 45s.
But it had ultimately decided to take a ‘precautionary’ in selecting who should get a booster job because of uncertainties in the modelling around how it would impact NHS winter pressures and what would happen if there was a more significant Covid-19 wave than expected.
Study lead Florence Halford from the UKHSA’s Covid- 19 Vaccines and Epidemiology Division said: ‘Covid-19 case fatality risk reduced after vaccination, with the lowest seen across all age bands when vaccinated up to six months prior to the specimen date.
‘This provides some evidence for continued booster doses in older age groups.’
This article first appeared in our sister publication Pulse