Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, on June 30, 2020.
  • People should keep wearing masks after getting a Covid-19 vaccine, Dr. Anthony Fauci said Thursday.
  • "We do not have enough data to be able to say with confidence vaccines can prevent transmission," Fauci said.
  • People who have received their vaccines in trials are being followed up to figure this out.
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People should keep wearing masks after receiving a Covid-19 shot because we don't yet know for sure that vaccines stop you spreading coronavirus, Dr. Anthony Fauci said Thursday.

"Even if vaccinated, you may still be able to pass on the virus to vulnerable people," Fauci, President Joe Biden's chief medical advisor, said in a tweet. "Masks are vital until we learn more and significantly reduce infections."

Clinical trials show the two Covid-19 vaccines authorized in the US - one from Moderna, one from Pfizer and BioNTech - are good at preventing symptomatic Covid-19, with full protection coming two weeks after receiving both doses. But we don't yet know how long protection from a vaccine lasts, or how well they prevent people from spreading the virus.

"Follow-up data are being collected from [Moderna and Pfizer] vaccine trial volunteers now," Fauci said. "If there are significantly fewer asymptomatic infections and a lower level of virus in the noses of vaccine recipients, it would suggest a decreased ability to transmit the virus following vaccination."

A small study that is under review by the Lancet, a leading medical journal, suggested that the Covid-19 vaccine co-developed by AstraZeneca and the University of Oxford had potential to reduce transmission in people with no symptoms. But the study was small, and more research is needed.

The single dose Covid-19 shot from Johnson and Johnson, which could get the green light from the Food and Drug Administration before the end of February, was good at preventing moderate to severe Covid-19 in studies. But again, we can't be sure it protects against passing on the virus to others.

Fauci, head of the National Institute of Allergy and Infectious Diseases, has also said people should wear two masks to minimize their risk of catching Covid-19. 

There are more than 26.6 million recorded coronavirus cases in the US, according to the Johns Hopkins University, and more than 485,000 people have died from Covid-19.

So far, roughly 35.2 million Covid-19 vaccines have been administered, with more than 6.9 million people fully immunized with two doses, according to the Centers for Disease Control and Prevention. 

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