LOS ANGELES - In a study of nearly 4,000 working adults, the Centers for Disease Control and Prevention found that vaccines reduced the risk of infection by 80% after one shot. The risk of infection was dropped even lower following a second dose.
"The risk of infection was reduced by 90% after individuals received two recommended doses of the vaccine. The study also finds that people started to get a protective effect even after the first shot," said CDC Director Rochelle Walensky.
The study involved roughly 4,000 individuals across six states. More than half were fully vaccinated with two shots.
Among 2,479 fully vaccinated participants, only three had become infected. Of the 477 people who had only received one dose, eight infections were reported compared to the 161 infections from 994 people who were not vaccinated at all.
"The study also demonstrated that two vaccines can reduce the risk of COVID-19 infections, not just in symptomatic infections, but also in asymptomatic or pre-symptomatic infections," added Walensky.
Participants employed in healthcare, emergency services and other essential work conducted weekly nasal swab tests regardless of symptoms.
The CDC report is the first to analyze how well the vaccines worked among front-line working-age adults who are at a higher risk of being exposed to the virus and spreading it.
Previously, both Pfizer and Moderna ran studies showing their vaccines had a 95 percent efficacy rate. The new government study conducted from mid-December to mid-March examines the shots across a wider scope of the population during a 13-week period when cases were spiking.