The protection offered by two doses of the Pfizer-BioNTech and the Oxford-AstraZeneca vaccines against COVID-19 begins to fade within six months, researchers in Britain stated highlighting the need for booster shots.
According to an analysis of data collected in Britain’s ZOE COVID study, after five to six months, the effectiveness of the Pfizer jab at preventing COVID-19 infection in the month after the second dose fell from 88 percent to 74 percent. For the AstraZeneca vaccine, effectiveness fell from 77 percent to 67 percent after four to five months.
The study was based on data from more than a million people, comparing self-reported infections in vaccinated participants with cases in an unvaccinated control group. Previous analysis of data suggested that vaccines protect for at least six months.
Under a worst-case scenario, protection could fall below 50 percent for older people and healthcare workers by the winter, Mr. Tim Spector, principal investigator for the ZOE COVID study, said.
“It’s bringing into focus this need for some action. We can’t just sit by and see the protectiveness slowly waning whilst cases are still high and the chance of infection still high as well,” Mr. Spector stated.
Britain and other European nations are planning for a COVID-19 vaccine booster campaign later this year after top vaccine advisers said it might be necessary to give third shots to the elderly and most vulnerable from September. The US government is also preparing to provide third booster doses starting in mid-September to Americans who had their initial course more than eight months ago.
Last week, a separate British public health study found that protection from either the Pfizer-BioNTech or the AstraZeneca vaccine against the now prevalent Delta variant of the coronavirus weakens within three months.