AstraZeneca COVID vaccine protection drops off after just 3 months, study reveals

EDINBURGH, Scotland — As breakthrough cases of COVID-19 rise this winter, a new report finds at least one version of the coronavirus vaccine loses its protective powers after just three months. Researchers from the University of Edinburgh say protection from the AstraZeneca vaccine drops off three months after a person receives their second dose.

Study authors examined data on 44 million patients in both Scotland and Brazil who received this version of the vaccine. In comparison to two weeks after their second shot (the point when doctors say vaccinations take full effect), the study finds people with the AstraZeneca vaccine are five times more likely to need hospitalization for COVID at the three-month mark.

Variants don’t matter

Researchers found that the dominant strain in each country was different, with Scotland dealing more cases of the Delta variant and Brazil seeing more patients with Gamma. Despite this, the results show the AstraZeneca vaccine’s effectiveness dropped off at a similar rate in both nations — meaning it’s likely the vaccine weakening rather than certain COVID variants breaking through.

Vaccines have been a key tool in fighting the pandemic, but waning in their effectiveness has been a concern for a while. By identifying when waning first starts to occur in the Oxford-AstraZeneca vaccine, it should be possible for governments to design booster programs that can ensure maximum protection is maintained. If eligible for a booster and you have not had yet had one, I would highly recommend that you book one soon,” says Professor Aziz Sheikh in a university release.

“Our analyses of national datasets from both Scotland and Brazil suggest that there is considerable waning of effectiveness for the Oxford AstraZeneca vaccine, with protection against severe COVID-19 falling over time. We studied two million people in Scotland and over 42 million people in Brazil who had received two doses of the Oxford-AstraZeneca vaccine,” adds Professor Vittal Katikireddi from the University of Glasgow.

“More than four months after receiving a second dose, the risk of experiencing either a COVID-19 hospitalization or death was approximately five times greater than the period of maximum vaccine protection after accounting for changes in infection rates and a range of other factors. Our work highlights the importance of getting boosters, even if you’ve had two doses of the Oxford AstraZeneca vaccine, as soon as you are able to.”

The team published their findings in The Lancet.

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