Pfizer and Moderna vaccines against COVID-19 they effectively prevented new coronavirus infections, not just diseases, with substantial protection evident two weeks after the first dose, U.S. government researchers said.
Two doses of the vaccine provide up to 90 percent protection against infection, according to data from a study by the U.S. Centers for Disease Control and Prevention (CDC) released Monday.
Previous clinical trials had established that vaccines also prevent disease, hospitalizations, and deaths.
The study adds to the evidence that new vaccines manufactured with messenger RNA technology they actually reduce the spread of viruses in real-world conditions. A previous study in Israel found that a single dose of the Pfizer vaccine reduced infections by up to 85 percent.
The CDC studied a group of approximately 4,000 front-line workers, including health care personnel, lifeguards, teachers, and service workers. from mid-December to mid-March, As vaccines were widely implemented.
These groups were among the first to be inoculated, along with vulnerable seniors, with their risk of virus exposure.
Participants were evaluated weekly for the SARS-CoV-2 virus and a survey was conducted to find out the symptom reports. The researchers compared the frequency of COVID-19 infections before and after vaccines to estimate how effective the injections were in preventing the spread of the pathogen, regardless of whether people felt sick or not.
Both Pfizer and Moderna vaccines require two separate doses per week. Two weeks after the first dose, injections appeared to prevent 80 percent of infections, which increased to 90 percent two weeks after the second dose, when people were considered completely immunized.