In December 2020, Israel began a mass vaccination campaign against COVID-19 administering the Pfizer BNT162b2 vaccine, which led to a sharp curtailing of the outbreak. After a period with almost no SARS-CoV-2 infections, a resurgent COVID-19 outbreak began in mid-June 2021. On July 30, 2021, a third (booster) dose of the vaccine was approved in Israel for individuals 60 years or older who had received the second dose at least five months previously. The booster vaccination campaign in Israel was gradually expanded to younger age groups who received a second dose five or more months earlier. Using Israel’s national database, we quantify the extent of waning immunity of two doses against the Delta variant, and estimate the difference in the rate of confirmed infection and severe COVID-19 between recipients of only two doses of vaccine and those also receiving a third booster dose. In this talk, I present the data, the methods used to analyze them, and the results that indicate the effectiveness of the booster dose for all age groups.
The work is joint with Micha Mandel, Yinon Bar-On, Omri Bodenheimer, Laurence Freedman, Sharon Alroy-Preis, Amit Huppert, and Ron Milo.