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, US government researchers said.
Two doses of vaccine provide up to 90% protection against infections, according to a study by the US Centers for Disease Control and Prevention (CDC) study released Monday.
Previous clinical trials had established that vaccines also prevent illness, hospitalization and death.
The study adds to the evidence that the new vaccines made with RNA messenger technology effectively reduce the spread of the virus under real conditions. A previous study in Israel found that a single dose of Pfizer vaccine reduced infections by up to 85%.
The CDC studied a group of about 4,000 front-line workers, including medical staff, nurses, teachers and service workers. from mid-December to mid-March, as vaccines have become widely implemented.
These groups were among the first to be inoculated, along with vulnerable elderly people, because of their risk of exposure to the virus.
Participants were tested weekly for SARS-CoV-2 virus and asked to report symptoms. The researchers compared the frequency of COVID-19 infections before and after vaccines to estimate how effective the injections were at preventing the spread of the pathogen, whether people felt bad or not.
Both Pfizer and Moderna vaccines require two separate doses per week. Two weeks after the first dose, the injections appeared to prevent 80% of infections, which increased to 90% two weeks after the second dose, when people were considered completely immunized.