Pfizer-BioNTech and Moderna Coronavirus vaccines are 94 percent effective at preventing symptomatic Covid-19 disease, according to a new study of 1,800 US healthcare workers.
The research the Centers for Disease Control and Prevention published on Friday provides even more evidence that the vaccines work well outside of controlled clinical trials.
“This report provided the most compelling information yet that Covid-19 vaccines are working as expected in the real world,” said Dr. Rochelle Walensky, CDC director, in a statement Friday.
“This study, which was added to the many previous studies, was instrumental in changing the CDC’s recommendations for those fully vaccinated against Covid-19.”
The results are based on an ongoing study of healthcare workers in 25 states. This interim analysis included data on 1,843 healthcare workers who were routinely tested for coronavirus infection. More than 80 percent of the participants were female.
About 623 workers tested positive between January and mid-March. Those who were fully vaccinated were 94 percent less likely to develop symptomatic coronavirus infections than their unvaccinated counterparts, the researchers found. The numbers are consistent with the effectiveness estimates from the clinical studies.
The scientists also found that a single dose of the two-shot regimen was 82 percent effective in preventing symptomatic infection. This number is higher than reported in other studies and may be due to the relative youth of the study participants, who had an average age of 37 to 38 years. Less than 2 percent were 65 years or older.
CDC scientists had previously found that fully vaccinated health, frontline, and essential workers were 90 percent less likely to contract the coronavirus. These results helped allay fears that vaccinated people might even asymptomatically transmit the virus and spread it to others.
Concern was a major reason for asking vaccinated Americans to continue wearing masks, a recommendation the CDC overturned Thursday.