Covid 19 coronavirus: Can vaccinated people spread the virus? We don’t know, scientists say

The US Centres for Disease Control and Prevention (CDC) has walked back controversial comments made by its director, Dr Rochelle 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 spokesperson told The New York Times on Friday.

“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.

The data suggest that “it’s much harder for vaccinated people to get infected, but don’t think for one second that they cannot get infected”, said Paul Duprex, director of the Centre for Vaccine Research at the University of Pittsburgh.

In a television interview with MSNBC’s Rachel Maddow, Walensky referred to data published by the CDC showing that one dose of the Moderna or Pfizer-BioNTech vaccine was 80 per cent effective at preventing infection, and two doses were 90 per cent effective.

That certainly suggested that transmission from vaccinated people might be unlikely, but Walensky’s comments hinted that protection was complete.

“Our data from the CDC 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.”

Walensky went on to emphasise 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.

Misinterpretation could disrupt the agency’s urgent pleas for immunisation, some experts said. As of Wednesday, 30 per cent of Americans had received at least one dose of a vaccine and 17 per cent were fully immunised.

Written by: Apoorva Mandavilli

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