PremiumCovid-19 vaccines are less effective against the Delta variant of coronavirus, according to a new UK study.
Pfizer Inc and BioNTech SE’s messenger RNA vaccine lost effectiveness in the first 90 days after full vaccination, though that shot and the one made by AstraZeneca Plc still staved off a majority of Covid infections, the study added.
The survey by the University of Oxford and the Office for National Statistics analysed over 3 million PCR tests from a random sample of people for a detailed picture of infection patterns as delta became the dominant variant this year.
“We’re seeing here the real-world data of how two vaccines are performing, rather than clinical trial data, and the data sets all show how the delta variant has blunted the effectiveness of both the Pfizer and AstraZeneca jabs," said Simon Clarke, an associate professor in cellular microbiology at the University of Reading.
Pfizer's shot remained less effective in comparison with AstraZeneca at preventing infections with a high viral burden in roughly 4.5 months after the second dose, said Koen Pouwels, an Oxford senior researcher who helped lead the study.
“The higher levels of virus that we’re seeing in these infections in vaccinated people are consistent with the fact that unvaccinated people are just going to be at higher risk, I’m afraid," said Sarah Walker, a professor of medical statistics and epidemiology at Oxford, who helped lead the study.
However, Penny Ward, a visiting professor in pharmaceutical medicine at King’s College London, who wasn’t involved with the study said that no vaccine is completely protected against infection with the delta variant.
He said at least Covid-19 vaccines are protecting individuals from developing severe Covid.
The results of the Oxford university's study might fuel calls to give booster shots to the fully vaccinated even as countries around the world still lack enough supply for first immunisations.
The US has already told its citizens that they would get a third dose of the vaccine after eight months.
Whereas UK authorities are still deciding how broadly boosters should be given. In Israel, which started giving third doses of Pfizer-BioNTech this month, initial results show they have been 86% effective for people over the age of 60.
(With Bloomberg inputs)
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