Need for masks necessary even after Covid-19 vaccine: Dr.Fauci

American physician and immunologistDr. Anthony Fauci said Thursday that even an effective Covid-19 vaccine won't replace the need for other public health measures, such as wearing a mask, social distancing and washing hands.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, said the vaccine will not be 100% effective and taken by 100% of the population -- which means there still will be room for Covid-19 to spread.

Fauci said he's being "practical" when he says, "I think if we can get 75 to 80% of the population vaccinated, I think that would be a really good accomplishment."

"It is not going to eliminate the need to be prudent and careful with our public health measures," he said in a Facebook Live conversation with New Jersey Gov. Phil Murphy.

Another reason to wear a mask: "There's good enough data to say that aerosol transmission does occur," Fauci told Murphy, meaning the virus can hang around in the air "for a period of time," instead of falling to the ground in larger droplets.

The Centers for Disease Control and Prevention is updating its guidance on airborne transmission of coronavirus after posting new recommendations Friday, only to revert to its earlier guidance Monday. The new message was posted in error, the CDC said.