However, the federal health authorities that manage the government’s syringe contracts told the FDA that more than 70 percent of the sites are using more efficient syringes and that more syringes can be bought or made according to another person who is aware of the situation.

Still, Pfizer’s attempts to pressurize the FDA worried some health officials, especially since the company itself originally calculated the vials contained five doses. If an extra dose could be extracted, it would mean the vaccine supply could be stretched, protecting more Americans from the virus. On the other hand, too few specialty syringes would mean the government could pay for wasted doses.

In early January, the debate was resolved after a “standard and customary legal review process,” said an FDA spokeswoman. On January 6, in a change to the emergency approval, the FDA officially changed the vaccine datasheet to specify six doses.

“Syringes and / or needles with low dead volume can be used to extract six doses from a single vial,” says the new US bulletin. It also warned, “If standard syringes and needles are used, there may not be enough volume to extract a sixth dose from a single vial.”

In a statement, an FDA spokeswoman said the agency considered several factors in approving Pfizer’s request, including the availability of the specialty syringes, the fact that other health officials had made a similar decision, and that the change would vaccinate Americans faster.

Pfizer and the federal government have agreed to keep track of which locations receive the syringes and other equipment needed to extract the extra dose, and that the company will not bill the US for six doses per vial for locations without these devices. According to a person familiar with the negotiations who was not allowed to speak because the conversations are confidential.

Beginning next week, the number of Pfizer vaccines the federal government will allocate to each state could be based on the assumption that each vial contains six doses, according to a federal official with no legal capacity to discuss the matter. The CDC and the Department of Health and Human Services did not discuss when they could do the shift until Friday afternoon.