Booster shot of Pfizer can cut mortality from Delta variant by 90%: Study

The third dose of the Pfizer COVID-19 vaccine can reduce mortality due to the Delta variant of the SARS-CoV-2 virus by 90 per cent, according to a study conducted in Israel.

The research, published in The New England Journal of Medicine on Thursday, included data from participants 50 years of age or older who had received two doses of Pfizer vaccine at least five months earlier.

The mortality due to COVID-19 among participants who received the booster during the study period (booster group) was compared with that among participants who did not receive the booster (non-booster group).

A total of 843,208 participants met the eligibility criteria, of whom 758,118 (90 per cent) received the booster during the 54-day study period, according to the researchers, including those from Clalit Health Services and Ben-Gurion University of the Negev, Israel.

Death due to COVID-19 occurred in 65 participants in the booster group (0.16 per 100,000 persons per day) and in 137 participants in the non-booster group (2.98 per 100,000 persons per day).

"Participants who received a booster at least five months after a second dose of Pfizer had 90 per cent lower mortality due to COVID-19 than participants who did not receive a booster," the authors of the study noted.

Among participants 65 years of age or older, death from COVID-19 occurred in 60 of 470,808 participants in the booster group and in 123 of 35,208 participants in the non-booster group, the researchers said.

In those younger than 65 years of age, death from COVID-19 occurred in 5 of 287,310 participants in the booster group and in 14 of 49,882 participants in the non-booster group, they said.

Among female participants, death from COVID-19 occurred in 54 of 400,300 participants in the booster group and in 13 of 47,972 participants in the non-booster group, according to the researchers.

The emergence of the Delta variant of SARS-CoV-2 and the reduced effectiveness over time of the Pfizer vaccine led to a resurgence of COVID-19 cases in populations that had been vaccinated early.

On July 30, 2021, the Israeli Ministry of Health approved the use of a third dose of Pfizer vaccine to cope with this resurgence.