The study analyzed 1.2 million Clalit members, including 600,000 who had received the Pfizer vaccine and 600,000 who had not. The inoculated group produced 94 percent fewer symptomatic COVID-19 cases, and 92 percent fewer cases of serious illness.
The vaccine, the study found, was equally effective for all age groups, including people aged 70 and older – a group for which Pfizer’s clinical trials had not produced conclusive data, as too few people of this age participated.
The vaccinated group included 170,000 people aged 60 and older and 430,000 people aged 16 to 59. The unvaccinated group was carefully chosen so that each person in the vaccinated group was matched with a similar person in the control group based on a long list of criteria, including risk of infection, risk of becoming seriously ill, general health and place of residence.