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British study shows COVID-19 vaccine efficacy wanes under Delta

19 August 2021 14:24 (UTC +04:00)

A British public health study has found that protection from either of the two most commonly used COVID-19 vaccines against the now prevalent Delta variant of the coronavirus weakens within three months, APA reports citing Reuters.

It also found that those who get infected after receiving two shots of either the Pfizer-BioNTech (22UAy.DE) or the AstraZeneca (AZN.L) vaccine may be of greater risk to others than under previous variants of the coronavirus.

Based on more than three million nose and throat swabs taken across Britain, the Oxford University study found that 90 days after a second shot of the Pfizer or Astrazeneca vaccine, their efficacy in preventing infections had slipped to 75% and 61% respectively.

That was down from 85% and 68%, respectively, seen two weeks after a second dose. The decline in efficacy was more pronounced among those aged 35 years and older than those below that age.

"Both of these vaccines, at two doses, are still doing really well against Delta... When you start very, very high, you got a long way to go," said Sarah Walker, an Oxford professor of medical statistics and chief investigator for the survey.

Walker was not involved in work on AstraZeneca's vaccine, which was initially developed by immunology experts at Oxford.

The researchers would not project how much more the protection would drop over time, but suggested that the efficacy of the two vaccines studied would converge within 4-5 months after the second shot.