The emergence of the delta variant of COVID-19 and the reduced effectiveness over time of the two-shot Pfizer vaccine led to a resurgence of COVID cases in populations that had been vaccinated early. In July 2021, the Israeli Ministry of Health approved the use of a third dose of the vaccine (also called a booster) to address this increase in COVID cases.
New data from Israel
In a new report from Israel, researchers collected data from older adults (aged 50 years or older) who had received two doses of Pfizer vaccine at least 5 months earlier. They compared the death rate due to COVID among participants who got the third booster shot to participants who did not receive the booster. Overall, among 843,208 participants, 90% received the booster during the 54-day study period. Also, almost 30% of participants had diabetes.
Striking reduction in risk of death from COVID with the Pfizer booster
Death due to COVID 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). In other words, there was a striking 90% reduction in death for those receiving booster shots (versus those who did not receive the booster). The study period for follow-up was 54 days. During this time, the incidence of COVID in Israel was one of the highest in the world.
In sum, participants who received a booster at least 5 months after a second dose of the Pfizer vaccine had 90% lower mortality due to COVID than participants who did not receive a booster. At the moment, we do not have similar data on other vaccines, but more research is planned.