The Centers for Disease Control and Prevention on Thursday walked back controversial comments made by its director, Dr. Rochelle P. Walensky, suggesting that people who are vaccinated against the coronavirus never become infected or transmit the virus to others.
The assertion called into question the precautions that the agency had urged vaccinated people to take just last month, like wearing masks and gathering only under limited circumstances with unvaccinated people.
“Dr. Walensky spoke broadly during this interview,” an agency spokesman told The Times. “It’s possible that some people who are fully vaccinated could get Covid-19. The evidence isn’t clear whether they can spread the virus to others. We are continuing to evaluate the evidence.”
The agency was responding in part to criticism from scientists who noted that current research was far from sufficient to claim that vaccinated people cannot spread the virus.
MSNBC’s Rachel Maddow, Dr. Walensky referred to data published by the C.D.C. showing that one dose of the Moderna or Pfizer-BioNTech vaccine was 80 percent effective at preventing infection, and two doses were 90 percent effective.
That certainly suggested that transmission from vaccinated people might be unlikely, but Dr. Walensky’s comments hinted that protection was complete. “Our data from the C.D.C. today suggests that vaccinated people do not carry the virus, don’t get sick,” she said. “And that it’s not just in the clinical trials, it’s also in real-world data.”
Dr. Walensky went on to emphasize the importance of continuing to wear masks and maintain precautions, even for vaccinated people. Still, the brief comment was widely interpreted as saying that the vaccines offered complete protection against infection or transmission.
In a pandemic that regularly spawns scientific misunderstanding, experts said they were sympathetic to Dr. Walensky and her obvious desire for Americans to continue to take precautions. It was only Monday that she said rising caseloads had left her with a sense of “impending doom.”