A study of about 600,000 vaccinated people in Israel found that the Pfizer-BioNTech vaccine remains highly effective at preventing symptomatic coronavirus infections under real-world conditions. The efficacy of the vaccine against moderate to severe/critical Covid-19 across all geographic areas was 66.9% at least 14 days after the single-dose vaccination and 66.1% at least 28 days after vaccination, according to the analysis. Pfizer and vaccine partner BioNTech are testing a third dose of their vaccine against the variants, the companies announced Thursday.