FDA approves U.S. emergency use authorization of Pfizer virus vaccine

WASHINGTON, DC -- The U.S. Food and Drug Administration on Friday night issued an emergency use authorization for Pfizer/BioNTech's coronavirus vaccine, calling it safe and strongly protective.

The EUA allows shipping to begin, but shots still can't be administered until the CDC's Advisory Committee on Immunization Practices (ACIP) meets and recommends the vaccine.

Dr. Amanda Cohn of the ACIP said its meeting would take place over the weekend.

The FDA approval comes a day after a panel advising the agency recommended it grant an emergency use authorization for the vaccine. It also came as the FDA commissioner was told to green light the vaccine by day's end Friday or resign, according to multiple sources.

Now that the FDA has authorized vaccine use, Operation Warp Speed -- the federal government's initiative to develop a vaccine -- can start distributing the vaccine to states.

Health and Human Services Secretary Alex Azar told ABC News that the FDA would work with Pfizer to get the vaccine shipped "so we could be seeing people get vaccinated Monday, Tuesday of next week."

With initial doses are scarce and rationed, governors are prioritizing who would get the vaccines first in their states. Healthcare workers and nursing home residents are first in line.

States will receive shipments of Pfizer's vaccine once a week to begin with after the shots are rolled out, Operation Warp Speed Chief Adviser Moncef Slaoui said.

The number of vaccines will increase "week-on-week" because manufacturing will ramp up, Slaoui said, adding that governors would be notified a week in advance how many doses to expect.

Enough vaccine for the general population isn't expected until spring, and experts urge people to mask up and keep their distance during a long, grim winter.

(ABC News, the AP and CNN contributed to this report.)