WASHINGTON (AP) — The U.S. government is close to a deal to acquire tens of millions of additional doses of Pfizer's vaccine in exchange for helping the pharmaceutical giant gain better access to manufacturing supplies.

A person with knowledge of the negotiations told The Associated Press on Tuesday that the deal is under discussion and could be finalized shortly. The person spoke on condition of anonymity to describe ongoing deliberations.

Pfizer's vaccine was the first to gain approval from the Food and Drug Administration and initial shipments went to states last week. It has now been joine...