Drugmaker Pfizer is expected to request authorization this week for an additional COVID-19 booster dose for seniors, according to a person familiar with the matter.

It would add a fourth dose to the regimen, which currently consists of a primary series of two shots, followed months later by a booster dose, in an effort to provide maximum protection to the over-65 population that has been hit hardest by the pandemic .

The Food and Drug Administration and the Centers for Disease Control must approve the request. The person who spoke about the upcoming Pfizer authorization request spoke on condition of anonymity because the person wasn’t authorized to speak on the record.

“We’re continuing to collect and assess all available data and we’re in continuous, open dialogue with regulators and health authorities to help inform a COVID-19 vaccine strategy as the virus evolves,” said Pfizer spokeswoman Jerica Pitts.

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Speaking to CBS’ “Face the Nation” on Sunday, Pfizer CEO Albert Bourla said, “Right now, the way that we have seen, it is necessary, a fourth booster right now. The protection that you are getting from the third, it is good enough, actually quite good for hospitalizations and deaths. It’s not that good against infections, but doesn’t last very long. But we are just submitting those data to the FDA and then we will see what the experts also will say outside Pfizer .”