Only half of the covid-19 vaccines delivered in the US have been used.

In Florida 76% of those vaccinated are white 3:08

(CNN) -

A possible explanation is emerging as to why federal data shows that only about half of the supply of covid-19 vaccines delivered in the US has been administered.

The U.S. covid-19 vaccine distribution figures have puzzled observers for weeks, with states saying they need more vaccines when data indicates they still have many doses on hand.

In Florida 76% of those vaccinated are white 3:08

President Biden's health officials tried to explain it Wednesday, at least in part.

At a news conference, Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, said that not all vaccines that are delivered to the states are available for "injecting into the arms. of people".

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White House covid-19 response coordinator Jeff Zients took that explanation a step further.

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"Some of what the states have right now is an inventory to do the very, very important second injection," Zients said.

"I think it's important that when you look at the state inventories you recognize that part of that inventory is being kept for the second dose."

The Pfizer and Moderna covid-19 vaccines currently available for emergency use in the US require two doses.

A federal board tracks the national distribution of these vaccines.

The data shows how many doses of vaccine have been administered in each state, but does not differentiate between the first and second doses.

States still have several doses of covid-19 vaccines, but reserve them for the second injection

For example in Florida, where federal data on Wednesday showed that about 3.1 million doses had been delivered and about 1.6 million had been administered.

That means that about 50% of the doses were injected.

On Monday, White House Press Secretary Jen Psaki used similar figures to suggest Florida had its fair share of vaccines, after Florida Governor Ron DeSantis claimed the state was not getting enough of the federal government and needed more.

"I'll note that since data comes first here, facts first, they have only distributed about 50% of the vaccines that have been given to them in Florida," said Psaki.

"So they clearly have a good amount of the vaccine."

On Wednesday, DeSantis dismissed those comments from the White House, explaining that the federal data did not take into account the vaccine intended for the second doses.

"When the person at the White House says Florida has all these doses, those are second doses," DeSantis said.

Other states also say that part of their vaccine inventory is destined for second injections.

“When a first dose comes, you can give it to someone.

When a second dose arrives, it should be 21 days later for Pfizer or 28 days later for Moderna, "said Kristen Ehresmann, director of the Minnesota Division of Epidemiology, Prevention and Control of Infectious Diseases in an email to CNN.

"So yeah, we get this vaccine and then we give it at the appropriate interval and it may seem like we're 'sitting around waiting when we have a lot of doses,' but that's not the case."

In New York, Governor Andrew Cuomo has begun expressing the state's vaccine distribution figures in terms of first and second doses, announcing on Wednesday that 96% of the first state-assigned doses have been administered, excluding the Federal long-term care facility vaccination program with CVS and Walgreens.

On Tuesday, Cuomo said his state was "basically out of vaccines," but that same day New York City Mayor Bill de Blasio, who had also complained about a vaccine shortage, said the city had doses to second injections in your inventory.

"I have 100,000 second doses," Blasio told MSNBC.

De Blasio went on to say that the doses were "on a shelf" and "cannot be used for weeks."

He said President Biden should direct governments across the country to take the second doses in their inventory and use them now for the first doses.

"Even a first dose gives people about 50% protection," he said.

Why not apply the saved doses of the vaccine?

Cuomo said Tuesday that second doses are not distributed as first doses due to uncertainty about how quickly additional doses of vaccine can be prepared.

'The fear is that until you really know what the production schedule is, if you start using the second dose as the first dose, we must have a dramatically increased supply, otherwise we will leave people without a second dose when it is. his moment, ”Cuomo said.

It is unclear how many states have a second dose inventory or how many states may be handling second dose distribution differently.

The White House and the Department of Health and Human Services did not immediately respond to CNN inquiries for additional details.

In Maryland, the state does not hold any reserve doses in its warehouses, other than doses that will be administered that week, according to Charles Gischlar of the state health department.

Gischalar says Maryland asked the federal government to automatically distribute second doses to providers who received the first doses.

CNN's Elizabeth Hartfield contributed to this story.

Vaccine