Delta variant: the effectiveness of the Pfizer vaccine decreases faster than that of AstraZeneca

The effectiveness of the Pfizer / BioNtech vaccine declines more rapidly than that of Oxford – AstraZeneca – against the Delta variant, according to a study conducted by researchers at the University of Oxford.

Before reaching this conclusion, British scientists, who co-produced one of the two sera, examined, between December 2020 and August 2021, samples taken from more than 700,000 people, reports Agence France-Presse (AFP ).

After one month, for infections with a high viral load, an individual who received his second dose of vaccine developed by the Pfizer laboratory was 90% more protected against the Delta variant of the coronavirus than an unvaccinated person.


After two months, this figure drops to 85%, and then to 78% after three months. Individuals who have received the two injections of the AstraZeneca vaccine are 67% protected after one month, 65% after two months and 61% after three months.

After four to five months, the level of protection of these two vaccines becomes similar, observed the authors of this study which, so far, has not been validated by peers.

These figures “really represent a decline” in effectiveness for Pfizer’s vaccine, said Dr. Koen Pouwels, who participated in this study, published this Thursday, August 19.

the efficacy of the two vaccines “remains very high”

Regarding the AstraZeneca vaccine, “the differences (from month to month) are due to chance, that is, there could be no change in protection”.

However, despite “these slight drops in protection,” said the doctor, “the overall effectiveness (of the two serums) remains very high”.

He also stressed that the researchers had studied the overall protection and not the level of protection against severe forms and hospitalizations, “two very important data to assess the effectiveness of vaccines.”

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