Updated August 9, 2022 at 7:22 PM ET
With the monkeypox vaccine still in short supply, the Biden administration is changing how the vaccine is administered in order to stretch its limited number of doses.
On Tuesday afternoon, federal health officials announced their decision to allow the JYNNEOS vaccine to be administered between layers of skin — what's known as an intradermal injection — rather than into the fat as is currently done.
By offering the shots in this way, only a fifth of the full dose is needed for each person.
To make the change, the Food and Drug Administration issued an Emergency Use Authorization to authorize the new dosing and injection strategy for the vaccine. (This follows last week's decision by the U.S. Department of Health and Human Services to declare monkeypox a Public Health Emergency, and an additional declaration today.)
"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," said FDA Commissioner Dr. Robert M. Califf. "This will increase the total number of doses available for use by up to five fold."
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Even with the change, a person will still need to receive two doses of the vaccine.
The FDA authorization also allows those under 18 who are considered at high risk of monkeypox infection to get the shot. However, that population will still receive the vaccine through subcutaneous injection — not the alternative method of injecting between layers of skin.
About 1.6 to 1.7 million people in the U.S. are considered at highest risk for the disease, but only about 1.1 million vaccine doses have been available, due to the expiration of vaccine reserves and delays in ordering replacements. Of those doses, about 670,000 have already been shipped to states and other jurisdictions.
Under the new dosing plan, the remaining 400,000 vials of vaccine will "have the potential to provide up to 2 million doses to Americans," said Robert Fenton, the White House monkeypox response coordinator.
The skin is home to a number of immune cells that trigger a potentially better immune response and this approach has been used with others vaccines, said Dr. Jon Andrus, an infectious disease specialist at George Washington University.
"It's actually a very good technique and it makes sense to go forward with it," he said.
But it also has challenges: It's harder to administer a vaccine in between layers of skin, and requires special training. Although this method has worked for polio and yellow fever, evidence that it will work for monkeypox is based on a single 2015 study.
Federal health officials ackowledge there are still questions about how well the monkeypox vaccine works.
"There is no traditional assessment of this vaccine," said Califf, adding that the vaccine was approved based on its "immunological response, not on clinical outcomes."
So far, there have been about 9,000 confirmed cases of monkeypox in the U.S., and that's likely an undercount given ongoing testing challenges.
"Right now, we need a lot of vaccine in a very short time period if we're going to get in front of this virus," said Anne Rimoin, an epidemiologist at UCLA. "And these vaccines are likely going to be very effective."
During this current outbreak, the vast majority of cases in the U.S. are occurring in gay and queer sexual networks, primarily among men who have sex with men.
Monkeypox causes lesions on the skin or mucous membranes. When the lesions rub up against another person's skin or mucous membranes, the virus can be transmitted, especially if the uninfected skin is damaged or broken. Most cases in the U.S. have been traced back to male-to-male sexual contact, according to the latest data from the Centers for Disease Control and Prevention.
It is possible for monkeypox to transmit nonsexually: people can catch the virus through face-to-face interactions with someone via respiratory droplets or by touching a surface that was contaminated. But data from this outbreak show these routes of transmission are extremely rare in public settings. When they do occur, it most likely happens when you live with an infected person and have prolonged contact with them.
"Gay, bisexual and other men who have sex with men in recent history have demonstrated significant confidence in vaccines, with COVID vaccination rates that are well over 90%," said Dr. Demetre Daskalakis, CDC's director of the division of HIV/AIDS and the White House monkeypox response deputy coordinator. "I think we're going to see that we will likely still run out of vaccines before we run out of arms."
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