Pfizer / BioNtech's vaccine is more effective in fighting infections linked to the Delta variant of the coronavirus than that of Oxford / AstraZeneca, but its effectiveness is declining faster, a British study revealed on Thursday.
To discover
Covid-19: what we know about the Delta variant
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Researchers at the University of Oxford, which co-developed one of the two sera, examined between December 2020 and August 2021 samples taken from more than 700,000 participants.
Loss of efficacy after three months
This analysis found that, for high viral load infections, an individual who received their second dose of Pfizer vaccine a month earlier was 90% more protected against the Delta variant than an unvaccinated person.
This figure drops to 85% after two months and then to 78% after three months.
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People 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 offered by the two vaccines becomes similar according to the study, which has not yet been validated by peers.
These figures "
really represent a decline
" in effectiveness for Pfizer's vaccine, explained Dr. Koen Pouwels, who worked on the study, while for AstraZeneca "
the differences (from month to month) are linked to chance, that is, there could be no change in protection
”.
Efficiency "remains very high"
The researcher nonetheless insisted on the fact that despite "
these slight drops in protection
", "
the overall efficacy (of the two vaccines) remains very high
", stressing that the researchers had studied the overall protection and not the level of protection. against severe forms and hospitalizations, “
two very important data for evaluating the effectiveness of vaccines
”.
The study comes as several countries, including the United Kingdom, are considering launching a booster campaign with a third dose of the vaccine.
The British government announced at the end of April that it had acquired 60 million new doses of the Pfizer vaccine in order to set up a booster program for the most vulnerable people in the fall.