Fauci: Public will know if third booster shot is needed by fall

The nation's top infectious disease expert Anthony FauciAnthony FauciThe Hill's Morning Report - Presented by Facebook - Cheney poised to be ousted; Biden to host big meeting Overnight Health Care: Biden announces 1M have enrolled in special ObamaCare sign-up period | Rand Paul clashes with Fauci over coronavirus origins | Biden vows to get 'more aggressive' on lifestyle benefits of vaccines Average US daily COVID-19 cases below 40K for first time since September MORE said Sunday that Americans should know if they need to get a third COVID-19 vaccine shot by this upcoming fall. 

During an appearance on ABC’s “This Week,” host Martha Raddatz asked Fauci about comments from Pfizer CEO Albert Bourla who suggested last week that vaccine recipients will "likely" need a third dose of its vaccine within six to 12 months after they've been fully vaccinated, with Moderna and Johnson & Johnson suggesting the same.

When asked when Americans would know for sure if they would need a third booster shot, Fauci said it would depend on when immunity would wane, which would likely be determined by summer or fall. 

"Yes, what you do, Martha, is you take a look at the level of what we consider a correlate of immunity, be it an antibody. And when the slope starts coming down, you could predict when you're going to get below the safe level, or you could start seeing breakthrough infections," Fauci said.

"I believe by the time we get to the end of the summer and the beginning of the fall, we'll have a pretty good idea whether we definitely or not need to get people boosts and when we need to give it to them," he added.

Bourla told CNBC’s Bertha Coombs at a CVS Health event last week that he predicts based on current data a “likely scenario” will involve the COVID-19 vaccine being administered to patients annually.