Pfizer Will Ship Fewer Covid-19 Vaccine Vials to Account for ‘Extra’ Doses

But federal health officials who manage the government’s contracts for syringes told the F.D.A. that more than 70 percent of the sites were using the more efficient syringes and that more could be easily bought or manufactured, according to another person knowledgeable about the situation.

Still, Pfizer’s attempts to pressure the F.D.A. unsettled some health officials, especially since the company itself originally calculated that the vials contained five doses. If an extra dose could be extracted, that would mean the vaccine supply could be stretched, protecting more Americans from the virus. On the other hand, too few of the specialty syringes would mean the government could end up paying for wasted doses.

By early January, the debate was resolved after a “standard and usual legal review process,” an F.D.A. spokeswoman said. On Jan. 6, in an amendment to the emergency authorization, the F.D.A. formally changed the vaccine’s fact sheet to specify six doses.

“Low dead-volume syringes and/or needles can be used to extract six doses from a single vial,” the new U.S. fact sheet read. It also warned, “If standard syringes and needles are used, there may not be sufficient volume to extract a sixth dose from a single vial.”

In a statement, an F.D.A. spokeswoman said that the agency considered several factors when agreeing to Pfizer’s request, including the availability of the special syringes, the fact that other health authorities had made a similar decision and that the change would vaccinate Americans more rapidly.

Pfizer and the federal government have agreed to track which sites are receiving the syringes and other equipment needed to extract the additional dose, and that the company will not charge the United States for six doses per vial at sites that don’t have that equipment, according to a person familiar with the negotiations who was not authorized to speak because the talks are confidential.

Beginning as soon as next week, the number of Pfizer vaccines that the federal government allocates to each state could be based on the assumption that each vial contains six doses, according to a federal official not authorized to discuss the matter. The C.D.C. and the Department of Health and Human Services were discussing as recently as Friday afternoon when they might make the shift.