Coronavirus updates: 1st vaccines now on the way to all 50 US states

Pfizer said it expects to have the vaccines rolling out of its Kalamazoo, Michigan, facility on Sunday morning.

The first shipments are expected to arrive at 145 sites on Monday, 425 sites on Tuesday and another 66 sites on Wednesday, Gen. Gus Perna of the Trump administration's Operation Warp Speed vaccine program said.

At those sites, the vaccines will be paired with ancillary kits to assist with the vaccinations. The kits contain needles, syringes, alcohol swabs, diluent, safety gear and vaccine reminder cards.

ABC News' Luis Martinez contributed to this report.

Common questions surrounding the newly authorized Pfizer vaccine include safety for teenagers and the risk of allergic reactions.

Though the final data doesn’t have conclusive data on 16 and 17 year olds because they weren’t enrolled in trials until more recently, the FDA is “very comfortable with the safety profile that was observed in 17 and 16 year olds," Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, told reporters.

Regarding allergies, Marks said 1.6% of the population has had a severe allergic reaction.

Marks said you should notify your doctor if you’ve ever had an allergic reaction to a vaccine and noted that sites that administer the vaccine will have medications on hand to respond to an allergic reaction.

ABC News’ Anne Flaherty contributed to this report.

FDA Commissioner Stephen Hahn on Saturday denied reports he was threatened with firing.

Sources familiar with the matter told ABC News that in a Friday phone call, White House chief of staff Mark Meadows suggested to Hahn that his job could be on the line if his agency didn’t authorize emergency use of the Pfizer-BioNTech vaccine by the end of the day.

“Representations in the press that I was threatened to be fired if we didn’t get it done by a certain date is inaccurate,” Hahn told reporters Saturday.

Hahn said he would “absolutely” take the Pfizer-BioNTech vaccine. He said it was authorized late Friday because science and data said it was ready, not because of “any other external pressure.”

ABC News’ Anne Flaherty contributed to this report.

A record number of people -- 3,309 -- died from COVID-19 Friday, according to new data from Johns Hopkins University.

Friday's record shattered the previous single-day record death toll of 3,124 which was set Wednesday.