Pfizer, Moderna Vaccines Highly Effective Even After 1st Shot: US Study

The risk of infection fell 90 per cent by two weeks after the second shot, the study of just under 4,000 people found.

COVID-19 vaccines developed by Pfizer Inc with BioNTech SE and Moderna Inc reduced the risk of infection by 80 per cent two weeks or more after the first of two shots, according to data from a real-world study of vaccinated US healthcare personnel and first responders released on Monday. The risk of infection fell 90 per cent by two weeks after the second shot, the study of just under 4,000 people found. The study by the US Centers for Disease Control and Prevention (CDC) evaluated the vaccines' ability to protect against infection, including infections that did not cause symptoms. Previous clinical trials by the companies evaluated their vaccine's efficacy in preventing illness from COVID-19. "This study shows that our national vaccination efforts are working," CDC Director Rochelle Walensky said in a statement.