We may soon be lining up to receive a fourth dose of a COVID-19 vaccine, at least according to the CEO of Pfizer.

One of three companies whose shots are currently approved for use in the U.S.

As it stands, only three doses are available to most Americans.

The first two give initial protection and the third boosts that coverage.

This three-shot regimen has been credited with helping stave of the Omicron surge.

Tens of millions of those doses came from Pfizer, but now the company is saying three shots is not enough going forward.

There is already some official backing to the idea of a fourth dose.

A study published by the Centers for Disease Control and Prevention last month- found vaccine effectiveness against severe cases fell to 66% among those who had received a third dose of either the Pfizer or Moderna vaccine.

Some countries are already recommending a fourth COVID-19 shot - for high-risk groups including Israel, Chile, and Germany.

Pfizer recently sent data to the Food and Drug Administration, so that the agency can examine whether a fourth shot is, in fact, needed.

Moderna is likewise working on a fourth shot.

Even still, it's expected that a decision on whether to approve them will take time.

Though officials have signaled that ruling could be expedited for those most at risk.