Arbel R, Hammerman A, Sergienko R, et al. - On July 30, 2021, the use of a third dose of BNT162b2 (booster) was approved in Israel by the Health Ministry to cope with the resurgence of coronavirus disease 2019 (Covid-19) cases in populations that had been vaccinated early. Researchers aimed at acquiring evidence suggesting the effectiveness of the booster in lowering mortality due to Covid-19.

• Among members of Clalit Health Services who were 50 years of age or older at the start of the study and had received two doses of BNT162b2 at least 5 months earlier, mortality due to Covid-19 was compared between those who received the booster during the study period (booster group) vs did not receive the booster (nonbooster group).

• There were a total of 843,208 participants meeting the eligibility criteria; 758,118 of these (90%) received the booster during the 54-day study period.

• Findings revealed 90% lower mortality due to Covid-19 among participants who received a booster at least 5 months after a second dose of BNT162b2 vs those who did not receive a booster.