WASHINGTON — After two months of a vaccine shortage that has undermined its response to the monkeypox outbreak, the Biden administration on Tuesday moved to stretch its limited supplies by authorizing a different injection method that will use one-fifth of the current dose.
At the same time, some promising news emerged from Denmark, where the world’s only producer of the main monkeypox vaccine, Jynneos, indicated that at least 200,000 doses previously thought to have expired might still be usable.
The developments suggest that the United States may be able to vaccinate hundreds of thousands more people at risk for monkeypox than anticipated by the end of the year. That could significantly help curb an outbreak that has infected nearly 9,000 Americans since May, and that some experts fear could spill over from high-risk groups to the broader population.
Injecting the vaccine between layers of the skin, instead of into the underlying fat, will be “a game changer when it comes to our response and our ability to get ahead of the virus,” said Robert J. Fenton Jr., the new White House monkeypox response coordinator, at a news briefing. “It’s safe, it’s effective, and it will significantly scale the volume of vaccine doses available.”
Federal officials estimate that the government can vaccinate up to five times as many people using so-called intradermal injection instead of the standard subcutaneous one. The government issued a public health emergency declaration, the second in less than a week, enabling the Food and Drug Administration to authorize the new regimen.
The F.D.A. also used its emergency powers to authorize the monkeypox vaccine for people under 18 who are at high risk of infection, citing an uptick in potential exposures in that age group. Previously, doctors had to ask the agency’s permission to vaccinate each child.
At least five children have been diagnosed with monkeypox, and dozens more are undergoing screening after an Illinois day care worker was found to be infected last week.
The United States once had more than 20 million doses of Jynneos in the national stockpile. It still owns 16.5 million doses of bulk vaccine, stored in freezers at the headquarters of the manufacturer, Bavarian Nordic, outside Copenhagen.
But the stockpile doses gradually expired over the past decade. After the outbreak began in mid-May, the government was slow to request that the bulk vaccine be processed into vials, ending up in a queue behind other countries that are also fighting monkeypox.
Now the Biden administration is scrambling to find a substitute firm that can bottle and label the bulk vaccine faster than Bavarian Nordic. It is also working with Bavarian Nordic to test whether some of the expired doses in the stockpile remain potent, even though the newest are already eight years old and at the end of their expected shelf life, according to firm’s chief executive, Paul Chaplin.
What to Know About the Monkeypox Virus
What to Know About the Monkeypox Virus
What is monkeypox? Monkeypox is a virus similar to smallpox, but symptoms are less severe. It was discovered in 1958, after outbreaks occurred in monkeys kept for research. The virus was primarily found in parts of Central and West Africa, but recently it has spread to dozens of countries and infected tens of thousands of people, overwhelmingly men who have sex with men.
Since monkeypox turned up here in May, the federal government has shipped local jurisdictions only 670,000 doses. Officials say they have roughly another half-million doses of the two-shot vaccine in hand. Those shots are enough to cover only about one-third of the 1.6 million to 1.7 million individuals the Centers for Disease Control and Prevention have identified as high risk. For now, the virus is primarily spreading primarily among men who have sex with men.
Changing the injection method appears to be the quickest fix for the shortage, although some experts said they worry that the data showing that will work is essentially limited to one study published in 2015 that was sponsored by the National Institutes of Health. Researchers compared the intradermal approach with the standard injection method and found the intradermal shots triggered a comparable level of neutralizing antibodies using one-fifth as much of the monkeypox vaccine. The intradermal shots also caused more redness, swelling and itching at the injection site.
At the briefing, Dr. Robert M. Califf, director of the F.D.A., called those side effects manageable. And Dr. Peter Marks, who oversees the agency’s vaccine regulation, said that a similar vaccine had been “given to thousands of people intradermally” in Germany in the 1970s. The method is “not at all new,” he said.
Federal officials are anxious for states and localities to adopt the new type of injection as quickly as possible, even though vaccinators are more familiar with the standard approach. Dr. Rochelle P. Walensky, director of the Centers for Disease Control and Prevention, said the agency is offering training seminars and other information to help bring vaccinators up to speed.
The federal government is also hoping that with doses that go farther, jurisdictions will no longer give people only the first of two shots in order to conserve supply. “There is data saying that is not protective enough,” Dr. Walensky warned. Research has shown that a single shot triggers a far weaker immune response that two.
Dr. Walensky also said that vaccinated individuals should continue “avoiding close skin-to-skin contact, including intimate contact, with somebody who has monkeypox because we don’t yet know how well these vaccines work.”
The Jynneos vaccine was licensed by the F.D.A. in 2019 for use against both monkeypox and smallpox without a large-scale clinical trial that studied effectiveness. Dr. Califf said none was conducted because there were never enough cases in the United States. Studies showed that, compared with an earlier, approved vaccine, Jynneos provoked a stronger immune response.
The intradermal method should diminish U.S. demand for new doses, which would presumably mean less profit for Bavarian Nordic. In a Tuesday morning interview, Mr. Chaplin, the company’s chief executive officer, said he hoped that the federal government would monitor at least some of those who are vaccinated intradermally to gather more safety data.
Since last Thursday, when federal officials first said they were considering the new method, he said, the company has been “bombarded” with calls from state officials asking how it would work, including how many times a vial could be punctured and how long the vaccine would remain potent once the seal on the vial had been broken.
“We’re now scrambling to try and get a hold of the C.D.C. and see what the official position will be because frankly, we don’t know,” he said. “We don’t know how long you can keep the vial once you puncture it.”
Mr. Chaplin also said that the company is busily testing samples of older doses that had sat for years in the government’s national stockpile, past their three-year expiration date. Up to a million doses that were manufactured in 2014 might still be usable, he suggested, but not for long.
“There is not a lot of time to hang around before we use them,” he said. “We’ve still got months, I would say.”
Some activists expressed concern that the White House was embracing what they viewed as relatively risky solutions to the shortage when it could use the government’s authority under the Defense Production Act to force an American company to bottle and label the bulk vaccine it owns.
“There are 15 million doses that they haven’t figured out how to get into vials, and instead they’re doing this really aggressive dose-sparing strategy,” said James Krellenstein, a Brooklyn-based gay health activist who has been urging federal health officials to expand access to the vaccine. He noted that the federal government has previously used the Defense Production Act to speed up aspects of Covid-19 vaccine production.
But vaccine production experts said that it would take an American company at least three months to gear up to handle the final manufacturing phase, known as fill and finish, regardless of how much pressure the White House exerted. Federal officials have been canvassing pharmaceutical companies for weeks, looking for one that will take on the work of vialing the bulk vaccine now stored in Denmark.
Noah Weiland contributed reporting.