A study from the University of Oxford claims that the vaccines from Pfizer/BioNTech and Oxford/AstraZeneca become less effective over time.
The Pfizer shot initially provides better protection than the AstraZeneca shot, preventing up to 85 percent of infections two weeks after the second vaccination. However, the effectiveness of the Pfizer vaccine declines more rapidly, dropping to 75 percent after 90 days. This is apparent from a preliminary print of the study carried out by researchers at the University of Oxford. Important footnote: The study has yet to undergo a peer review.
The AstraZeneca vaccine is still 61 percent effective against coronavirus infection 90 days after the second shot. A smaller decrease, because this vaccine offers 68 percent protection against Covid-19 shortly after vaccination.
“After four to five months, protection by the two vaccines is comparable”
The culprit of the declining effectiveness would mainly be the Delta variant of the coronavirus that is ubiquitous. Still, two doses of Covid vaccine remain the best way to provide protection.
“After about four to five months, the two vaccines should be comparable” in how much protection they provide, said Sarah Walker, a professor of medical statistics and epidemiology at the University of Oxford who is also the principal investigator for the National Covid-19 Infection Survey. of the United Kingdom.
The Oxford study looked at infections after taking 2.5 million test sticks from early December to August. The authors emphasized that both vaccines are highly effective against the Delta variant, even if the efficacy of the Pfizer shot declines more rapidly.
Virus particles in nose and throat
Penny Ward, a professor of pharmaceutical medicine at King’s College London, wrote in a statement that the Oxford study could support calls for booster injections for people who have received two mRNA injections (the Pfizer vaccine is and mRNA vaccine). . She also suggested that people who have received two doses of the AstraZeneca vaccine could receive an mRNA shot to “improve protection against this variant as winter approaches.”
The researchers conclude that after an infection with the Delta variant, vaccinated people have just as many virus particles in their nose and throat as non-vaccinated people. “This allows group immunity a greater challenge become”, says the Dutch researcher and co-author of the study Koen Pouwels.
“Vaccines are probably the best at preventing severe disease, but slightly less effective at preventing transmission of the virus.”
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