LONDON (Reuters) – The protection against Covid-19 offered by two doses of the Pfizer/BioNTech and Oxford/AstraZeneca vaccines starts to wane within six months, underlining the need for booster doses, according to researchers at the United Kingdom.
The British study ZOE Covid pointed out that, in the case of the Pfizer/BioNTech vaccine, the effectiveness one month after the second dose, which is 88%, drops to 74% after five to six months. As for AstraZeneca’s immunizing agent, the effectiveness dropped from 77% a month later to 67% after four or five months.
The study was based on data from more than one million app users, comparing self-reported infections in vaccinated participants with cases in an unvaccinated control group.
More data from younger people is needed, because participants vaccinated up to six months ago tend to be older, as this age group was prioritized when the first vaccines were approved, the study authors said.
ZOE Ltd was founded three years ago to provide personalized nutrition guidance based on exam sets. The company’s ZOE Covid Symptom Study app is a non-profit initiative in collaboration with King’s College London and funded by the Department of Health and Welfare.
In a future worst-case projection, protection could drop to less than 50% for older people and health care professionals by winter, said Tim Spector, co-founder of ZOE Ltd and the study’s lead investigator.
“He’s calling attention to the need for some action. We can’t just wait to see protection slowly diminish while cases are still high and the chance of infection is still high,” Spector told the BBC.
The UK and other European nations are planning a booster Covid-19 vaccine campaign later this year since senior vaccine advisers said it may be necessary to administer third doses to the elderly and the most vulnerable starting in September.
The US government is preparing to offer third booster shots from mid-September to Americans who received their initial shots more than eight months ago.
“This is a reminder that we can’t rely on vaccines alone to prevent the spread of Covid,” said Simon Clarke, an associate professor of cell microbiology at the University of Reading who was not involved in the study.
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