Real-world CDC study finds approved mRNA vaccines 94 percent effective against COVID-19

The results of a real-world Centers for Disease Control and Prevention (CDC) study of 1,843 health workers across the United States showed last week that COVID-19 mRNA vaccines authorized by the U.S. Food and Drug Administration (FDA) are 94 percent effective.

Currently approved mRNA vaccines are those produced by Moderna and Pfizer-BioNTech. While their effectiveness was previously studied in clinical trials, this independent assessment was conducted on a larger sample size and a broader geographic area of 25 states, confirmed their efficacy in the wild.

“This report provided the most compelling information to date that COVID-19 vaccines were performing as expected in the real world,” CDC Director Rochelle Walensky said. “This study, added to the many studies that preceded it, was pivotal to CDC changing its recommendations for those who are fully vaccinated against COVID-19.”

Participants who tested positive for SARS-CoV-2 were examined against those who tested negative. From the 1,843 participants, 623 positive cases were identified. Estimates were made by comparing the odds of COVID-19 vaccination in positive cases and negative cases. With that in mind, symptomatic illness was reduced by 94 percent among health care workers who were fully vaccinated and by 82 percent among those who were even partially vaccinated.

Healthcare workers were chosen for the study due to their higher risk for exposure to SARS-CoV-2 from patient interactions.

FDA-authorized COVID-19 vaccines continue to be assessed by the CDC through surveillance networks, allowing the agency to see how well the vaccines manage in the real world. This will be particularly important in the days ahead, as the FDA just last week authorized the expansion of vaccination protocols to include adolescents 12 years old through 15 years old.