US health officials have cleared a plan to expand the nation’s limited supply of monkeypox vaccine by giving people just one-fifth the usual dose, citing research that suggests the reduced amount is nearly as effective.
The so-called dose-sparing approach also requires administering the Jynneos vaccine by injection just under the skin, rather than into deeper tissues, a practice that may better activate the immune system. Recipients will still receive two shots four weeks apart.
The highly unusual step is a stark acknowledgment that the US currently lacks the supplies needed to vaccinate everyone seeking protection from the rapidly spreading virus.
Federal officials estimate that about 1.6 million to 1.7 million Americans are at the highest risk of the disease, mostly men with HIV or men who have a higher risk of contracting it. Vaccinating this group would require more than 3.2 million shots.
White House officials said the new policy would immediately multiply the 440,000 currently available as full doses into more than two million smaller doses.
People line up at a monkeypox vaccination site in Encino, California, on July 28. Officials say giving smaller doses of the vaccine to Americans means 400,000 doses could be stretched into more than two million doses. (Marcio Jose Sanchez/Associated Press)
“It’s safe, it’s effective, and it will greatly increase the volume of vaccine doses available to communities across the country,” Robert Fenton, the White House’s monkeypox response coordinator, told reporters.
CBC News contacted Health Canada to ask if it is considering reducing the size of the doses to expand its supply of the same vaccine, which in Canada goes by the trade name Imvamune. Just over 1,000 cases of monkeypox have been confirmed in Canada.
Different vaccination technique
Smaller doses also require a different type of injection that penetrates only the top layer of skin, not the bottom layer between the skin and the muscle. This is a less common technique that may require additional training for some healthcare professionals. But infectious disease specialists said that shouldn’t be much of a hurdle.
“Intradermal administration is certainly something that has been used for other vaccines, including the smallpox vaccine, which was administered to hundreds of millions of people in the 20th century,” said Anne Rimoane, director of UCLA’s Center for Global and Immigrant Health. .
The shallower injection is thought to help stimulate the immune system because the skin contains many immune cells that target external invaders.
A man receives a monkeypox vaccine at an outdoor clinic in Montreal on July 23. (Graham Hughes/The Canadian Press)
The CDC said it will provide educational materials about the technique along with a broader awareness campaign to US health departments.
The Biden administration declared monkeypox a public health emergency last week in an effort to slow the outbreak, which has infected more than 8,900 Americans.
Officials announced a separate decision Tuesday that allows the Food and Drug Administration to expedite its review of medical products or new uses for them, such as the dose-saving technique for Jynneos.
The FDA has cleared the approach for adults 18 and older who are at high risk of monkeypox infection. Younger people can also get the vaccine if they are considered high risk, although they must get the traditional shot, the agency said.
“Strong immune response” to a smaller dose
Regulators pointed to a 2015 study showing that inoculation with one-fifth of the traditional two-dose vaccine generated a strong immune system response comparable to that of the full dose. About 94 percent of people receiving the smaller dose had adequate levels of virus-fighting antibodies, compared with 98 percent of those receiving the full dose, according to a study funded by the National Institutes of Health.
The NIH is planning an additional trial of the technique. Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said her agency is already beginning to track the vaccine’s real-world effectiveness in American communities, although initial estimates will take time to generate.
A nurse prepares a dose of monkeypox vaccine in Salt Lake City, Utah, on July 28. The US estimates that 1.6 million to 1.7 million Americans are at highest risk of the disease, mostly men with HIV or men who are at higher risk of contracting it. (Rick Baumer/Associated Press)
But some experts and advocates worry that, with little data to support the policy, it could backfire if it makes the vaccine less effective.
“We have serious concerns about the limited amount of research that has been done on this dose and method of administration, and we fear that this will give people a false sense of confidence that they are protected,” said David Harvey of the National Coalition of STD Directors , in a statement.
Scaling of vaccine doses is common in Africa and other parts of the world with limited health resources. In recent years, the World Health Organization has endorsed the strategy to deal with outbreaks of yellow fever, polio and other diseases.
“This is not an unusual situation,” said Dr. William Moss of the Johns Hopkins Vaccine Access Center. “It all comes down to public health decision-making: During an epidemic, when you don’t have enough supplies, do you make that trade-off?”
Both the UK and Canada have adopted a single-dose vaccine strategy, prioritizing people who face the highest risk of monkeypox. And health departments in several major US cities have adopted a similar strategy amid tight supplies, including New York, San Francisco and Washington.
US officials have sent more than 625,000 full doses of the vaccine to state and local health departments. Until now, vaccinations have been recommended for people who have already been exposed to monkeypox or are likely to get it due to recent sexual contact in areas where the virus spreads.
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In its latest update on July 23, Health Canada said it had sent more than 70,000 doses of vaccine to provinces and territories. CBC News has requested additional information on Canada’s vaccine stockpile and its ability to meet demand for immunizations, with some provinces already distributing doses.
Imvamune is usually an injection with two doses given 28 days apart, with the option of a booster two years later.
But in guidelines for health professionals released in mid-JuneOntario said it will use a “ring vaccination approach” and offer only one dose in areas with confirmed cases – given the “current limited supply” of vaccines.
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