Pfizer, Moderna highly effective in real-world U.S. study: CDC
The risk of infection fell 90% by two weeks after the second shot, the study of just under 4,000 vaccinated U.S. healthcare personnel and first responders found.
The study by the U.S. 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.
The findings from the real-world use of these messenger RNA (mRNA) vaccines confirm the efficacy demonstrated in the large controlled clinical trials conducted before they received emergency use authorizations from the U.S. Food and Drug Administration.
The study looked at the effectiveness of the mRNA vaccines among 3,950 participants in six states over a 13-week period from Dec. 14, 2020 to March 13, 2021.
"The study found that the risk of infection was reduced by 90% after individuals received those two recommended doses of the vaccine," Walensky said. "The study also found that people start getting a protective effect after the first dose. The risk of infection decreased by 80% after two weeks," she added.
The new mRNA technology is a synthetic form of a natural chemical messenger being used to instruct cells to make proteins that mirror part of the novel coronavirus. That teaches the immune system to recognize and attack the actual virus.
The CDC study comes weeks after real-world data from Israel suggested that the Pfizer/BioNTech vaccine was 94% effective in preventing asymptomatic infections.
