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Pfizer vaccine: protection against infection decreases after two months

Two medical studies published Wednesday confirm that the immune protection provided by the Pfizer-BioNTech vaccine wanes after only two months, but protection against the severe form of the disease, hospitalizations and death remains important.

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The two studies from Israel and Qatar and published in the New England Journal of Medicine, support the arguments that even fully vaccinated people should maintain barrier gestures, physical distancing and wearing a mask.

The Israeli study was carried out on 4,800 people working in the health field, and shows that the antibodies decrease rapidly after two doses of vaccines, and in particular in men, in people 65 years of age or over and in immunocompromised people.

“Published work on many vaccines, such as those against measles, mumps and rubella, has shown a small decrease of 5-10% each year in neutralizing antibody levels,” the researchers say in the publication.

For Pfizer’s COVID vaccine, “we found that a significant and rapid decrease in the humoral response was observed in the months following vaccination.”

The study also indicated that the immunity of people vaccinated after infection with COVID-19 lasts longer than in people who have never had the disease.

The second study conducted in Qatar looked at actual infections among the highly vaccinated population of this small Gulf country, mostly with Pfizer.

“Protection against infection induced by [vaccin Pfizer] accumulates rapidly after the first dose, peaks in the first month after the second dose, then gradually decreases over the following months, ”wrote Laith Abu-Raddad of Weill Cornell Medicine-Qatar and colleagues.

“The decline in protection seems to accelerate after the fourth month to reach a low level of around 20% in the following months,” they added.

Nonetheless, protection against hospitalizations and death remained above 90%, they said.

The decreasing protection may be linked to the behavior of the population, they noted.

“Vaccinated people likely have a higher rate of social contact than unvaccinated people and may also have less adherence to health measures,” they wrote.

“This behavior could reduce the actual efficacy of the vaccine relative to its biological efficacy, possibly explaining the decline in protection.”

These new studies warn that new pandemic waves could occur in the coming weeks, months, given the decline in protection.

“These results suggest that a large portion of the vaccinated population could lose their protection against infection in the months to come, possibly increasing the potential for further epidemic waves,” the researchers write.

Pfizer has argued that the immunity of the first two doses of its vaccine begins to wane after a few months.

Last month, Pfizer got clearance from the Food and Drug Administration (FDA) in the United States to give booster doses of its vaccine about six months after people finished their first two doses.

In Israel, a third dose of vaccine is required to be considered adequately vaccinated.

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