Dr. Anthony Fauci warns "it's not going to be a light switch" back to normalcy even when a COVID-19 vaccine becomes available to the public.

In fact, Fauci recommends people still wear masks and practice social distancing even after getting the vaccine, he told CNN's Jake Tapper on "State of the Union" on Sunday.

On Monday, Moderna announced that preliminary data showed the COVID-19 vaccine it developed in collaboration with the National Institute of Allergy and Infectious Diseases is more than 94% effective. The news follows a similar announcement from Pfizer and BioNTech on Nov. 9, which showed their COVID-19 vaccine was above 90% effective.

"Obviously, with a 90-plus percent effective vaccine, you could feel much more confident" about not getting the virus, Fauci told Tapper. "But I would recommend to people to not abandon all public health measures just because you have been vaccinated." Those fundamentals include: universal wearing of masks, maintaining physical distance, avoiding large crowds, doing more outdoor activities and washing hands frequently.

Because "even though, for the general population, it might be 90[%] to 95% effective," said Fauci, "you don't necessarily know, for you, how effective it is." Even at those success rates, about 5% to 10% of people immunized may still get the virus.

"In addition, the protective effect of a vaccine may take at least one month, if not slightly longer," says Dr. David Ho, a virologist working on developing monoclonal antibody therapies for COVID-19 at Columbia University. (So far, Pfizer said early results showed its two-dose vaccine showed 90% effectiveness seven days after the second dose. Early data on Moderna's two-dose vaccine showed 94.5% efficacy two weeks after the second dose.)

"Therefore, for the foreseeable future, we will need to continue our mitigation measures, including wearing masks," Ho says, noting that precautionary measures will likely last "for much of 2021."

Dr. Bruce Hirsch, an infectious disease specialist at Northwell Health, adds that many people have strong feelings about vaccines and may not take them, which "will impact the general population from being immune to COVID-19 and prolong the threat of the pandemic."

It is worth noting that as the trials for both vaccines progress, efficacy numbers could change, and it is also not yet clear how long any immunity would last.

Fauci, 79, said when it is his turn to get vaccinated, he doesn't plan on abandoning all the public health measures that he has been advocating during the pandemic.

"I could feel more relaxed, in essentially not having the stringency of it that we have right now, but I think abandoning it completely would not be a good idea," Fauci told Tapper.

Fauci predicted to Tapper that most of the country will get vaccinated in the second or third quarter of 2021. But "we are not going to turn [the pandemic] on and off, going from where we are to completely normal. It's going to be a gradual accrual of more normality as the weeks and the months go by, as we get well into 2021," he said.

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