The Pfizer-BioNTech and Moderna COVID-19 vaccines are working in the real world, according to a new federal study of 3,950 health care and essential workers that confirms both vaccines provide 90 percent protection against coronavirus infections two weeks after the second dose.
The Centers for Disease Control and Prevention (CDC) findings mirror how effective the vaccine manufacturers said their products were based on extensive clinical trials. The U.S. Food and Drug Administration (FDA) used the data from the clinical trials when it granted emergency use authorizations (EUA) to both vaccines, which were developed using mRNA technology, in December 2020.
CDC conducted the study by following health care workers, first responders and other essential workers in parts of six states (Arizona, Florida, Minnesota, Oregon, Texas and Utah). The participants in the study tested themselves weekly from December 14, 2020, though March 13, 2021. CDC officials said they were more likely than the general population to be exposed to the virus because of the work they do.
The study also showed that even after one dose, these vaccines offer substantial protection. Both were 80 percent effective two weeks after the first shot. The study was able to detect evidence of any coronavirus infection, whether or not the participants had any symptoms.