CDC: Vaccines working against new infections
The coronavirus vaccines made by Moderna and Pfizer-biontech are proving highly effective at preventing symptomatic and asymptomatic infections under real-world conditions, federal health researchers reported Monday.
Consistent with clinical trial data, a two-dose regimen prevented 90 percent of infections by two weeks after the second shot. One dose prevented 80 percent of infections by two weeks after vaccination.
The news arrives even as the U.S. rapidly broadens eligibility for vaccines and the average number of daily shots continues to rise. The seven-day average of vaccines administered hit 2.7 million Sunday, a slight increase over the pace the previous week, according to the Centers for Disease Control and Prevention.
But the virus may be gaining renewed momentum. According to a New York Times database, the seven-day average of new virus cases as of Sunday was 63,000, an increase of more than 16 percent over the past two weeks.
Similar upticks over the summer and winter led to major surges in the spread of disease, CDC Director Dr. Rochelle Walensky said at a news briefing Monday.
The nation has “so much reason for hope,” she said. “But right now I’m scared.” Walensky added that she felt a sense of “impending doom.”
Scientists have debated whether vaccinated people may still get asymptomatic infections and transmit the virus to others. The new study, by CDC researchers, suggested that because infections were so rare, transmission is likely rare, too.
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 because they were health care workers, first responders or others on the front lines. None had previously been infected with the coronavirus.
Most — 62.8 percent — received both shots of the vaccine during the study period, and 12.1 percent had one shot.
The investigators also asked participants about symptoms associated with infection, including fever, chills, cough, shortness of breath, sore throat, diarrhea, muscle aches, or loss of smell or taste. The researchers also analyzed patients’ medical records to detect illnesses.
Fifty-eight percent of the infections were detected before people had symptoms. Just 10.2 percent of infected people never developed symptoms.