WASHINGTON — It sounded like a simple solution to the monkeypox vaccine shortage: Just by changing the way doses are injected, the federal government could vaccinate five times as many people with the supplies it has on hand.
But the approach — injecting one-fifth of the current dose into the skin instead of a full dose into the underlying fat — isn’t really that simple, experts say. And some federal officials are concerned about changing the method without more research, although Dr. Robert M. Califf, head of the Food and Drug Administration, described Thursday’s proposal as promising.
Some outside experts are also urging 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 many things in life, in science, that we think should work, but when we actually do them, they don’t.”
Stretching doses of the vaccine, Jynneos, could help the federal government solve a predicament partly of its own making. Despite investing more than $1 billion in developing the two-dose vaccine to be used against both monkeypox and smallpox, the government has only 1.1 million vaccines on hand, in part because it has been slow to order mass stockpiles of the vaccine. to be processed into vials.
That amount is enough to cover 550,000 people, but about three times as many doses are needed to cover the 1.6 million to 1.7 million Americans who, according to the Centers for Disease Control and Prevention, are at high risk of monkeypox. So far, the virus is primarily spread through skin-to-skin contact during sex among gay and bisexual men, the CDC 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 can quell the outbreak before it spreads more widely.
But some experts argue that this approach has not been studied enough. They also warn that some vaccinators will need training to properly administer the shots, which could slow vaccination efforts. Otherwise, the government may waste doses rather than save them.
Intradermal injection involves carefully guiding a needle into the layers of the skin, a thin space with immune cells. If the vaccinator goes too deep and inserts the dose into fat, the patient may not get enough vaccine, experts say. But if the needle is not inserted far enough, some of the vaccine may leak back.
“If you’re giving a lower dose and you’re not injecting it right into the skin — you might be injecting it in the wrong place — you might not be getting a protective vaccine,” said Dr. Phil Krause, who retired as the FDA’s senior vaccine regulator last year and working on licensing Jynneos from the agency. “If you’re asking it to be done across the country in millions of doses, it’s much easier to have errors in the administration of the vaccine.”
On the other hand, the method has experience. It was used in polio vaccination campaigns when doses were limited, and in skin tests for rabies and tuberculosis.
What you need to know about the monkeypox virus
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What is monkeypox? Monkeypox is a virus similar to smallpox, but the symptoms are milder. It was discovered in 1958 after an outbreak in monkeys kept for research. The virus was found mostly in parts of central and west Africa, but in recent weeks it has spread to dozens of countries and infected tens of thousands of people, mostly men who have sex with men. On July 23, the World Health Organization declared monkeypox a global emergency.
How is it spread? The monkeypox virus can spread from person to person through close physical contact with infectious lesions or pustules, by touching objects—such as clothing or bedding—that have previously been in contact with the rash, or by respiratory droplets produced by coughing or sneezing. Monkeypox can also be transmitted from mother to fetus through the placenta or through close contact during and after birth.
I’m afraid I might have monkey pox. What should I do? There is no way to get tested for monkeypox if you only have flu-like symptoms. But if you start to notice red lesions, you should contact an urgent care center or your primary care doctor, who can order a monkeypox test. Isolate at home as soon as you develop symptoms and wear high-quality masks if you need to come into contact with others for medical care.
I live in New York. Can I get the vaccine? Adult men who have sex with men and have had multiple sexual partners in the past 14 days are eligible for the vaccine in New York, as are close contacts of infected people. Eligible people who have diseases that weaken the immune system or who have a history of dermatitis or eczema are also strongly encouraged to get vaccinated. People can book an appointment through this website.
“This is not an entirely new concept,” said Dr. Anthony S. Fauci, President Biden’s chief medical adviser. “We thought of this as a vaccine shortage strategy years ago.”
Vaccinators used special bifurcated needles in smallpox inoculation campaigns that allowed them to perform intradermal injections more evenly and cheaply.
Dr. John Beagle, associate director of clinical research at the National Institutes of Health, said a government-sponsored study of Jynneos published in 2015 compared the intradermal approach with the standard injection method and found it produced a comparable level of neutralizing antibodies, a measure of the strength of the immune response. The intradermal method causes more redness, swelling and itching, but the standard injection is more painful.
Dr. Bagel said that switching to an intradermal method is a better option for preserving the vaccine than giving only one shot, as some jurisdictions do now, because research shows that a single shot does not produce nearly as strong an immune response.
“One dose probably won’t be effective,” he said, adding that the intradermal method “is an acceptable way.”
Although the 2015 trial included hundreds of participants, some experts note that it was a single study that was limited in what it measured. NIH researchers planned to test the intradermal strategy for Jynneos in a trial that was set to begin in a few weeks. But results weren’t expected until late fall or early winter, and that plan is up in the air for now.
Dr. H. Clifford Lane, clinical director of the NIH’s Dr. Fauci National Institute of Allergy and Infectious Diseases, said that while researchers can gather insight by following people who get vaccinated, a traditional clinical trial would provide -clear picture.
“I understand doing it as long as it’s very clear why it’s being done,” he said of the intradermal strategy. “The question is: How can we increase the current supply without significantly compromising efficacy?”
How well the vaccine will work is another question. It was licensed in 2019 for use against both monkeypox and smallpox after studies showed it provoked a stronger immune response than a previous vaccine. The drug itself was approved because it compared favorably to an even earlier vaccine, federal officials said.
Monkeypox is rarely fatal and no deaths have been reported in the United States. Symptoms usually resolve within two to four weeks. But as the outbreak has spiraled from eight reported cases in late May to 7,510 now, the administration is trying to improve vaccination rates and the availability of tests and treatments.
Currently, the epidemic is almost entirely confined to men who have sex with men, with those who have multiple partners considered to be particularly at risk. But five cases involving children have been reported so far. On Friday, the Illinois Department of Public Health announced that an adult working at a daycare center had tested positive for monkeypox and that children and other staff members there were being screened.
Thursday’s declaration of a public health emergency allowed the federal government to speed up monkeypox investigations and approve grants, but did not invoke the FDA’s emergency powers. Changing the injection regimen would require a second type of emergency declaration, giving the Food and Drug Administration more leeway to issue emergency use authorizations.
Federal regulators can issue emergency authorizations for products when they believe the potential benefits outweigh the potential risks. At the start of the coronavirus pandemic, the Trump administration issued the same type of emergency declaration, allowing the FDA to provide Covid-19 vaccines to Americans many months before regulators issued full approvals.
Dr. Calif, the FDA commissioner, said Thursday that regulators will continue to ensure that the vaccine is delivered in a safe and effective way. He said regulators would likely decide in the next few days whether to proceed with the intradermal strategy, but that it “looks good right now” — a comment that some outside experts said appeared to preempt the career regulators’ deliberations.
Emily Cochrane and Tracy Tully contributed reporting.
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