“The protection that you are getting from the third, it is good enough, actually quite good for hospitalizations and deaths,” he said, according to a CBS News transcript. “It’s not that good against infections, but doesn’t last very long.”

Also read: Two years of COVID-19: How the pandemic changed the way we shop, work, invest and get medical care

A second booster has already been approved for some immunocompromised people.

Bourla said he expects the COVID booster to become an annual occurrence, much like the flu shot, and added that Pfizer is working on a vaccine that offers even better protection.

“So what we are trying to do, and we are working very diligently right now, it is to make not only a vaccine that will protect against all variants, including omicron, but also something that can protect for at least a year. And if we be able to achieve that, then I think it is very easy to follow and remember so that we can go back to really the way used to live,” he said.

Bourla also said he expects data on the Pfizer vaccine’s effectiveness for children 5 and under to be ready in April, which — if positive and approved — would put the first vaccinations on track for May.

In February, Pfizer and its partner BioNTech SE
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unexpectedly delayed seeking federal authorization for the vaccine to be used on young children. On Sunday, Bourla said he understands the frustration of parents, but that the delay had “good intent.”

Pfizer “eventually concluded that the best thing to do for the kids, it is the way to have a full set of data that provides full, transparent proof about what the vaccine can do,” he said. “I think the three doses likely will provide a very strong set of evidence.”