WASHINGTON (NewsNation Now) — Dr. Anthony Fauci says vaccinated Americans would “not necessarily” need to get booster shots this fall for further protection from COVID-19.

Fauci, the nation’s leading infectious disease expert, told CBS “This Morning” on Friday that scientists would be tracking data on the virus and possible variants. He says it was still “possible” an additional shot would be needed later this year to ward off possible infection.

“We are planning for the eventuality that we might have to boost people. We don’t know whether we will have to do it and when we will have to do it,” said Fauci.

Pfizer and Moderna are giving a more specific date, saying COVID-19 booster shots could be needed by September.

Pfizer’s CEO explained people who are vaccinated might need a booster shot within eight to 12 months.

For people who got the Pfizer vaccine, that would mean a third shot following their initial two-doses.

The president of Moderna recently told investors there could be a need for a booster shot every nine to 12 months to prevent severe illness from COVID-19.

Clinical trials for both are currently underway.

Fauci also urged Americans to continue following CDC guidelines. He stressed those who haven’t been fully vaccinated still need to wear masks even if they are largely spending time with people who have been inoculated.

The doctor also says those attending indoor sporting events, like the NBA playoffs, starting this week, should follow the masking policies of the arena.

In the meantime, President Joe Biden is still pushing his goal to get 70% of American adults at least one shot by July 4th.

Right now, 60% have at least one dose which adds up to more than 160 million people according to the CDC.

The president says that means between now and independence day, 20 million more Americans have to roll up their sleeves.