Two weeks after the second dose of the Pfizer-BioNTech coronavirus vaccine is given, it is 99% effective in preventing symptomatic COVID-19 and 91.2% in preventing infection.

The data is among the findings of an analysis of the electronic health records of 1.7 million Israelis. Conducted by Maccabi Health Services and the Technion – Israel Institute of Technology, the study shows the effectiveness of the Pfizer vaccine gradually increasing starting at 12 days after the first dose and reaching maximum effectiveness at around 35 days (about two weeks after the second dose).

Effectiveness was the same for men and women, but declined “mildly but significantly with age” – particularly after age 80 – and for patients with specific chronic comorbidities, most notably type 2 diabetes” and also conditions including heart or lung disease, the authors wrote.