EXPLAINER: How much COVID-19 vaccine will be shipped in US

NEW YORK (AP) — COVID-19 vaccines have begun shipping in the U.S. after getting emergency authorization, setting off the nation's biggest ever vaccination push. But supplies are expected to be limited for some time.

The first wave of shipments is going to health care workers and nursing home residents. Officials say vaccines should be available to everyone by the middle of next year.

Trucks with Pfizer’s vaccine rolled out Sunday. They will deliver to 145 distribution centers around the country by Monday, said Army Gen. Gustave Perna of Operation Warp Speed, the government effort to develop and distribute COVID-19 vaccines. An additional 425 sites will get shipments Tuesday, and the remaining 66 on Wednesday.

For now, only Pfizer's vaccine, which the Food and Drug Administration greenlit Friday, is being shipped. Another vaccine by Moderna will be reviewed by an expert panel this week and could get the go-ahead soon afterward.

Other vaccines also could follow.

HOW MANY SHOTS WILL BE SHIPPED OUT INITIALLY?

Around 3 million.

When states were told their first-round allocations earlier this month, the figures were based on the 6.4 million Pfizer doses that were ready for distribution at the time, Perna said. Since the Pfizer vaccine requires two doses, the government is holding back the second shots to ensure people can get them.

An additional 500,000 doses are being held in reserve for any emergencies, Perna said.

HOW MUCH VACCINE IS EACH STATE GETTING?

U.S. officials say it's based on a state’s population of people 18 and older. Federal officials haven't released a breakdown, but some states have shared their initial allocations.

Colorado, for example, says it's supposed to get 46,800 doses of the Pfizer vaccine in the first round, with more expected in the weeks...