BNT162b2 Vaccine Booster Reduced COVID-19-Related Mortality in People Aged ≥50 Years in Israel

December 9, 2021

By Denise Baez

People aged 50 years and older who received a booster at least 5 months after a second dose of the BNT162b2 vaccine had 90% lower mortality due to coronavirus disease 2019 (COVID-19) than participants who did not receive a booster, according to a study published in The New England Journal of Medicine.

Ronen Arbel, PhD, Clalit Health Services Headquarters, Tel Aviv, Israel, and colleagues obtained data for all members of Clalit Health Services (CHS) who were 50 years or older and had received 2 doses of the BNT162b2 vaccine at least 5 months earlier. CHS covers approximately 52% of the Israeli population and is the largest of 4 healthcare organisations in Israel that provide mandatory healthcare.

Participants were excluded if they had been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or had received a booster before August 6, 2021, which was 7 days after the approval of the booster for use in persons aged 60 years or older in Israel.

A total of 843,208 participants met the eligibility criteria, of whom 758,118 (90%) received the booster during the 54-day study period. Death due to COVID-19 occurred in 65 participants in the booster group and in 137 participants in the non-booster group. The adjusted hazard ratio (aHR) for death due to COVID-19 in the booster group versus the non-booster group was 0.10 (95% confidence interval [CI], 0.07-0.14; P < .001).

In the Cox regression model, age, male sex, chronic kidney failure, lung cancer, and history of cerebrovascular accident were confounding variables that had a significant association with death due to COVID-19.

The hazard ratio for death due to COVID-19 in participants up to 7 days after the administration of the booster, as compared with the -group, was 0.95 (95% CI, 0.86-1.05; P = .32). However, the hazard ratio for death due to COVID-19 in participants up to 14 days after the administration of the booster, as compared with the non-booster group, was 0.67 (95% CI, 0.60-0.74; P < .001).

“Therefore, our assumption of a 7-day lag time between the administration of the booster and booster effectiveness was confirmed,” the authors wrote.

The researchers also conducted a subgroup analysis among participants aged 65 years or older. In those aged 65 years and older, death due to 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 (aHR = 0.09; 95% CI, 0.07-0.13; P < .001). Among participants aged 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 (aHR = 0.13; 95% CI, 0.04-0.40; P < .001).

Overall, during the study period, confirmed SARS-CoV-2 infection was observed in 2,888 participants in the booster group and in 11,108 participants in the non-booster group (aHR = 0.17; 95% CI, 0.16-0.18; P < .001).

“Our study showed that among people aged 50 years or older who had received a second dose of the BNT162b2 vaccine at least 5 months earlier, those who received a booster had 90% lower mortality due to COVID-19 than those who did not receive a booster,” the authors wrote. “The waning vaccine effect that was observed in Israel and in other populations that had been vaccinated early may occur in upcoming months in many other populations, in concordance with the timing of the first 2 doses of BNT162b2 in the mass vaccination campaign. Nevertheless, regulatory approval or recommendation of the booster, especially for people younger than 65 years, is still under debate in many countries. The evidence generated in this study, which shows significant lifes-aving potential from providing the booster, may help to resolve this issue.”

The primary limitation of the study was the relatively short study period (54 days). However, during this time, the incidence of COVID-19 in Israel was one of the highest in the world and social-distancing restrictions in Israel were limited. Therefore, exposure to SARS-CoV-2 was substantial, and accordingly, the number of deaths due to COVID-19 was sufficient to show a significant association between the use of the booster and lower mortality due to COVID-19. In addition, the study’s findings are limited to the BNT162b2 vaccine; ongoing research comparing other vaccines may provide insight on this issue.

“Another major limitation of the study is the lack of data regarding serious adverse events,” the authors wrote. “Future studies will be needed to assess the safety of the administration of the booster.”

Reference: https://www.nejm.org/doi/full/10.1056/NEJMoa2115624

SOURCE: The New England Journal of Medicine