(NEXSTAR) – The CEO of Pfizer said it’s “likely” that Americans will need a third shot 12 months after getting fully vaccinated.

Albert Bourla’s comments were taped April 1 but released by CNBC Thursday.

Bourla also said it’s probable that a COVID-19 vaccine will be needed annually, similar to the flu shot.

“It is extremely important to suppress the pool of people that can be susceptible to the virus,” he told CNBC.

He also said that vaccines are an essential tool against variants.

Bourla’s statement follows Johnson & Johnson CEO Alex Gorsky’s February comments that individuals may need to get vaccinated against COVID-19 each year.

On Thursday, David Kessler, the White House COVID response chief science officer, said Americans should expect to receive annual booster shots to protect against variants.

Variants, he said, “challenge” the effectiveness of the vaccine.

“We don’t know everything at this moment,” he added.

Both Pfizer and Moderna have said their vaccines are 95% effective at preventing severe COVID-19 infection six months after full vaccination.

It remains to be seen how long the shots will fend off coronavirus after that six-month mark.