(The Hill) — The Biden administration on Tuesday announced a new strategy to stretch the limited available doses of the Jynneos monkeypox vaccine by changing how the vaccine is injected.

The new method would split up the doses and use one-fifth as much vaccine per shot. The partial dose of the vaccine would be injected into the upper layer of skin, rather than the full dose into the underlying fat, which is how shots are typically administered.

The strategy was first outlined last week by Food and Drug Administration (FDA) Commissioner Robert Califf, who said the intradermal injection method would allow officials to administer more shots without compromising the safety or effectiveness of the vaccine.

“In recent weeks the monkeypox virus has continued to spread at a rate that has made it clear our current vaccine supply will not meet the current demand,” Califf said in a statement Tuesday. “By increasing the number of available doses, more individuals who want to be vaccinated against monkeypox will now have the opportunity to do so.”

In order to allow the FDA to authorize the new strategy, the Department of Health and Human Services first issued a determination allowing the agency to take emergency measures based on the information currently available about the monkeypox virus.

The Biden administration is scrambling to try to control the spiraling monkeypox epidemic, which has become both a political and public health concern. More than 8,900 cases have been reported, and experts think that’s likely an undercount. 

The move is aimed at alleviating a major shortage of Jynneos, the only FDA-approved vaccine for monkeypox. The administration has hundreds of thousands of doses available but will need millions more to vaccinate the 1.6 million gay and bisexual men officials consider to be at the highest risk for the virus 

White House Monkeypox Response Coordinator Bob Fenton on Tuesday called the move a “game changer.” He said the 400,000 vials currently in the Strategic National Stockpile now have the potential to provide up to 2 million doses.  

“It’s safe, it’s effective, and it will significantly scale the volume of vaccine doses available for communities across the country,” Fenton told reporters during a briefing.

The Biden administration is under intense criticism for its response to the outbreak. Critics say officials were too slow to ship the vaccine that was ready to use, and even slower to recognize the magnitude of the outbreak in order to get more shots ready to use.    

The U.S. has already purchased much of the global supply of Jynneos, but much of it is stored frozen in bulk substance at the manufacturer in Denmark. It needs to undergo a process called “fill and finish” to put the vaccine into usable vials to be shipped and then administered.

Intradermal injection is not a new method, but the evidence on its effectiveness with Jynneos— and using a dose one-fifth the normal size — is limited at best. It’s also a much more difficult method of vaccination, and will likely require additional training.

Some outside experts said the strategy makes sense, while others were not convinced.

Monica Gandhi, an infectious disease expert and professor of medicine at UC San Francisco, said the idea of dose splitting is a known strategy to make vaccines last longer. It’s been studied with influenza vaccines, rabies vaccines and some tuberculosis vaccines, she said.

“We are in this situation, at this moment, we are in a time of scarcity. We have more people who need the vaccine than have it,” Gandhi said. “We have to figure out how to get people the vaccine.”

She added that U.S. officials likely realize they made mistakes, and are reaching for any strategy they can to try to fix the situation.

“We can’t we can’t go back in time. We have to just do work with what we have until we can get more vaccines,” Gandhi said, adding that she would have advised the administration to implement the same strategy.

But some experts and advocates are concerned about the lack of data to support the new policy.

“We have grave concerns about the limited amount of research that has been done on this dose and administration method, and we fear it will give people a false sense of confidence that they are protected,” David Harvey, executive director of the National Coalition of STD Directors said in a statement. “This approach raises red flag after red flag, and appears to be rushed ahead without data on efficacy, safety, or alternative dosing strategies.”