Protection against Covid-19 by BNT162b2 Booster across Age Groups

Background:After promising initial results from the administration of a third(booster)dose of the BNT162b2 messenger RNA vaccine(Pfizer-BioNTech)to persons 60 years of age or older,the booster campaign in Israel was gradually expanded to persons in younger age groups who had received a second dose at least 5 months earlier.Methods:We extracted data for the period from July 30 to October 10,2021,from the Israel Ministry of Health database regarding 4,696,865 persons 16 years of age or older who had received two doses of BNT162b2 at least 5 months earlier.In the primary analysis,we compared the rates of confirmed coronavirus disease 2019(Covid-19),severe illness,and death among those who had received a booster dose at least 12 days earlier(booster group)with the rates among those who had not received a booster(nonbooster group).In a secondary analysis,we compared the rates in the booster group with the rates among those who had received a booster 3 to 7 days earlier(early postbooster group).We used Poisson regression models to estimate rate ratios after adjusting for possible confounding factors.