LONDON (Reuters) – The protection against COVID-19 offered by two doses of the Pfizer/Bioantek and Oxford/AstraZeneca vaccines begins to wear off within six months, underscoring the need for booster doses, researchers in the United Kingdom said.
The British ZOE Covid study indicated that in the case of the Pfizer/BioNTech vaccine, efficacy drops a month after the second dose, which is 88%, to 74% after five to six months. For AstraZeneca’s fortifying agent, its effectiveness decreased from 77% after one month to 67% after four or five months.
The study was based on data from more than one million users of the app, comparing self-reported infections in vaccinated participants with cases in the unvaccinated control group.
The study authors said more data from young people is needed, because participants who were vaccinated six months earlier tended to be older, as this age group was prioritized when the first vaccines were approved.
ZOE Ltd was founded three years ago to provide personalized nutritional guidance based on test suites. The company’s ZOE Covid Symptom Study app is a non-profit initiative in association with King’s College London and funded by the Department of Health and Welfare.
In anticipating the worst case in the future, protection could drop below 50% for seniors and healthcare professionals by winter, said Tim Spector, co-founder of ZOE Ltd and lead investigator on the study.
It draws attention to the need for some action. “We can’t 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 countries are planning a booster vaccine campaign for Covid-19 later this year, with top vaccine advisers saying a third dose may be necessary 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 first shots more than eight months ago.
“This is a reminder that we cannot rely on vaccines alone to prevent the spread of Covid,” said Simon Clark, associate professor of cellular microbiology at the University of Reading who was not involved in the study.
“Friendly zombie guru. Avid pop culture scholar. Freelance travel geek. Wannabe troublemaker. Coffee specialist.”