Booster shot of Pfizer vaccine can cut mortality from Delta variant by 90%, says Israeli study

Data culled from 54-day study period involving 8 lakh participants aged over 50, some of whom had got the booster shot.

A nurse fills a syringe with a dose of the Pfizer Inc.-BioNTech SE Covid-19 vaccine | Bloomberg

New Delhi: The third, or ‘booster’, dose of the Pfizer-BioNTech vaccine can reduce mortality due to the Delta variant of the SARS-CoV-2 by as much as 90 per cent, according to a new study by researchers from Israel.

For the study, published in The New England Journal of Medicine, researchers obtained data for over eight lakh participants over 50 years of age who had received two doses of BNT162b2 at least five months earlier. The number of deaths due to Covid-19 among participants who received the booster during the 54-day study period was compared with the mortality among participants who did not receive the booster dose. 

A total of 8,43,208 participants met the eligibility criteria, of whom 7,58,118 — that is 90 per cent — received the booster during the study period. 

In the booster group, 65 participants died due to Covid-19, while 137 deaths were reported in the group that did not receive any boosters. 

Based on the data, researchers concluded that participants who received a booster at least five months after a second dose of BNT162b2 had 90 per cent lower mortality due to Covid-19 than participants who did not receive a booster.

Sharp drop, then Delta spike

The team pointed out that the incidence of Covid-19 dropped from almost 1,000 cases in a million people a day in January 2021 to only one-two daily cases in a million persons in June 2021. 

However, the emergence of the Delta variant and the reduced efficacy of BNT162b2 over time led to a resurgence of Covid-19 cases in Israel.

By August 2021, Israel had the highest incidence of Covid-19 worldwide. On 30 July 2021, the Israeli Ministry of Health approved the use of a third dose (booster) of the BNT162b2 vaccine (Pfizer-BioNTech’s mRNA vaccine), in response to the resurgence of Covid cases in the country driven by the B.1.617.2 (Delta) variant. 

The booster was initially approved for use in persons aged 60 years or above who had received a second dose at least five months earlier. Two weeks later, the age of eligibility was lowered to 50 years. 

The approval was made despite the lack of robust evidence of the efficacy of a Pfizer vaccine booster shot and the absence of regulatory approval by the US Food and Drug Administration and by the European Medicines Agency. 

(Edited by Saikat Niyogi)