March 29 (UPI) -- The two-dose COVID-19 vaccines from Pfizer-BioNTech and Moderna lower the risk for infection in healthcare workers and first responders by up to 90%, according to data released Monday by the U.S. Centers for Disease Control and Prevention.
Among healthcare workers, first responders and other essential workers who received both doses of the one of the vaccines, which were developed using similar technology, risk of infection was reduced by 90% two or more weeks after inoculation, the data showed.
Even two weeks after those studied received the first dose of a two-dose vaccine, the risk of infection dropped by 80%, the agency said.
"The authorized ... COVID-19 vaccines provided early, substantial real-world protection against infection for our nation's healthcare personnel, first responders and other front-line essential workers," CDC Director Dr. Rochelle P. Walensky said in a press release.
"These findings should offer hope to the millions of Americans receiving COVID-19 vaccines each day and to those who will have the opportunity to roll up their sleeves and get vaccinated in the weeks ahead," she said.
The analysis assessed the effectiveness of the Pfizer-BioNTech and Moderna vaccines in preventing infections among 3,950 clinicians, police, fire and EMS staff and other front-line personnel in six states over a 13-week period from Dec. 14, 2020, to March 13.
These groups are more likely than the general population to be exposed to the virus because of their occupations, according to the CDC.
Among the study participants, 63% received both doses of either of the vaccines within the study period, while another 12% received only one dose.
Because it takes about two weeks after each dose of vaccine for the body to produce antibodies that protect against infection, people are considered partially vaccinated two weeks after their first dose and fully vaccinated two weeks after their second dose, the CDC said.
Three of the 2,479 fully vaccinated participants and eight of the 477 partially vaccinated participants tested positive for COVID-19 following inoculation.
Meanwhile 161 of 989 unvaccinated participants became infected, according to the CDC.
The findings demonstrate that the vaccines reduce the risk for infection, not just symptomatic disease, the agency said.
"This study shows that our national vaccination efforts are working," Walensky said.
"The authorized vaccines are the key tool that will help bring an end to this devastating pandemic," she said.