Covid: Against the Delta variant, Pfizer and Moderna vaccines are only 66% effective

Published by Manon C. · Updated on 26 August 2021 at 15h26 · Published on 25 August 2021 at 10h00
According to a study published this August 24, 2021 by the American health authorities, Pfizer and Moderna are no longer 91% effective but 66% effective against the Delta variant.

According to the latest data published in a study this Tuesday August 24, 2021 by the American health authorities, Pfizer and Moderna vaccines effectiveness drops from 91% to 66% against the Delta variant. In the U.S. the Delta variant – more contagious than the previous strains – has been dominating since the beginning of July and is causing 98% of the contaminations.

The study was carried out in thousands of hospital staff members and care centers in 6 states in the U.S. Tested weekly, participants have been given the Pfizer and Moderna vaccines. The study shows that between December and April 2021, both serums were 91% effective, according to data published by the CDC.

But since the Delta variant has taken over in the United States, their effectiveness dropped from 91% to 66%. “Although these interim findings suggest a moderate reduction in the effectiveness of COVID-19 vaccines in preventing infection, the sustained two thirds reduction in infection risk underscores the continued importance and benefits of COVID-19 vaccination”, the study authors specify.

The latter assess the vaccine effectiveness fades over time, as we now know. Furthermore, the American health authorities have announced a booster-shot vaccination campaign for third doses starting from mid-September 2021, targeting at American adults who have been given the second dose 8 months earlier.

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