Officials debate whether to allow new monkeypox vaccination strategy

A new way to inject the monkeypox vaccine could boost the nation's vaccine supply, but some experts say the approach doesn't hasn't been studied enough.

WASHINGTON — It looked like a simple solution to the monkeypox vaccine shortage: simply by changing the way the doses are injected , the federal government could vaccinate five times as many people with the supply it has on hand.

But the approach - injecting a fifth of the current dose into the skin instead of a full dose in the underlying fat - is not so simple, experts say. And some federal officials are worried about changing the method without more research, even though Dr. Robert M. Califf, the head of the Food and Drug Administration, on Thursday called the proposal promising.

Some outside experts also urge caution. "From a basic science perspective, it should work," said Dr. Jay K. Varma, director of the Cornell Center for Pandemic Prevention and Response. "But, of course, there are a lot of things in life, in science, that we think should work, and when we actually do them, they don't."

Expanding doses of the vaccine, Jynneos, could help the federal government resolve a predicament partly of its own making. Despite investing more than a billion dollars in developing the two-dose vaccine to be used against both monkeypox and smallpox, the government only has 1.1 million vaccines on hand, in partly because it has been slow to order bulk vaccine stocks to be made into vials.

This supply is enough to cover 550,000 people, but it takes about three times as many doses to cover the 1.6 million to 1.7 million Americans who the Centers for Disease Control and Prevention say are at high risk for monkeypox. For now, the virus is mainly spread through skin-to-skin contact during sex among gay and bisexual men, according to the C.D.C. said.

Some federal officials hope that by injecting a smaller dose of the vaccine between the layers of the skin, called an intradermal injection, the Biden administration could stem the epidemic before it spreads more widely.

But some experts say this approach has not been studied enough. They also warn that some vaccinators will need training to administer vaccines correctly, which could slow vaccination efforts. Otherwise, the government could end up wasting doses, not saving them.

Intradermal injection involves carefully guiding a needle through the layers of the skin, a thin space with immune cells. If a vaccinator goes too far and inserts the dose into the fat, the patient might not get enough vaccine, experts say. But if the needle is not inserted far enough, some of the vaccine may leak out.

"If you give a lower dose and don't inject it not properly in the skin — you might inject it in the wrong place — you might not give a protective vaccine,” said Dr. Phil Krause, who retired as senior F.D.A. vaccine regulator the year last and worked on the agency license for Jynneos." If you're asking for it to be done nationwide in millions of doses, it's much easier for there to be mistakes made in the administration of the vaccine."

On the other hand, the method has proven itself. It has been used in polio vaccination campaigns when doses were limited, as well as for rabies and tuberculosis skin testing.

"This is not a brand new con ept," said Dr. Anthony S. Fauci, President Biden's chief medical adviser. "We thought of it as a strategy in case of vaccine shortages years ago."

Vaccinators have used special bifurcated needles in inoculation campaigns against smallpox that allowed them to perform intradermal injections more consistently and at lower cost.

Dr. John Beigel, associate director of clinical research at the National Institutes of Health, said