The Pfizer/BioNTech and Moderna COVID-19 vaccines have been shown to decrease the risk of COVID-19 infection by 80% two weeks or more following the first dose in data obtained from a real-world U.S. study.

The study included around 4,000 U.S. healthcare personnel and first responders and revealed that the risk of infection declined by 90% by two weeks following the second dose. The real-world data from the use of these mRNA vaccines confirm the efficacy seen in large controlled clinical trials conducted before emergency use authorizations were given by the U.S. Food and Drug Administration. The findings endorse previous studies that suggested that the vaccines started working soon after the first dose, and verify that they prevent asymptomatic infections as well… (Reuters, March 30, 2021)