The Atlanta Journal-Constitution
■ The coronavirus vaccines made by Moderna and Pfizer are proving highly effective at preventing infections in real-world conditions, researchers say,
Participants who got Pfizer, Moderna twice show few infections.
The coronavirus vaccines made by Moderna and Pfizer-biontech are proving highly effective at preventing symptomatic and asymptomatic infections in real-world conditions, federal health researchers reported Monday.
Consistent with clinical trial data, a two-dose regimen prevented 90% of infections by two weeks after the second shot. One dose prevented 80% of infections by two weeks after vaccination.
There has been debate over whether vaccinated people can get asymptomatic infections and transmit the virus to others. The study, by researchers at the Centers for Disease Control and Prevention, suggested that transmission may be extremely unlikely.
There also has been concern that variants may render the vaccines less effective. The study’s results do not confirm that fear. Troubling variants were circulating during the time of the study — from Dec. 14 to March 13 — yet the vaccines still provided powerful protection.
The CDC enrolled 3,950 people at high risk of being exposed to the virus. None had been infected.
Most — 62.8% — received both shots of the vaccine in the study, and 12.1% had one shot. Participants collected their own nasal swabs each week, which were sent to a central location for PCR testing. The swabs allowed researchers to detect asymptomatic infections as well as symptomatic ones.
Fifty-eight percent were detected before people had symptoms, and 10.2% of infected people never developed symptoms.
Among those fully vaccinated, there were .04 infections per 1,000 person-days, meaning among 1,000 persons there would be .04 infections in a day, compared with 0.19 infections per 1,000 person-days among those who had one dose. In contrast, there were 1.38 infections per 1,000 person-days in unvaccinated people.