U.S. health officials have authorized a plan to stretch the limited supply of monkeypox vaccine in the country by giving people just one-fifth the usual dose, citing research that suggests the reduced amount is almost as effective.
The so-called dose-sparing approach also calls for the Jynneos vaccine to be given by injection just under the skin rather than into deeper tissue, a practice that may better rev up the immune system. Recipients would still receive two injections four weeks apart.
The highly unusual step is a clear acknowledgment that the US currently lacks the supplies needed to vaccinate everyone seeking protection against the rapidly spreading virus.
Federal officials consider about 1.6 million to 1.7 million Americans to be at highest risk of contracting the disease, primarily men with HIV or men who are at increased risk of contracting it. Vaccinating that group would require more than 3.2 million injections.
White House officials said the new policy would immediately multiply the 440,000 full doses currently available into more than two million smaller doses.
“It is safe, effective, and will significantly scale the volume of vaccine doses available to communities across the country,” Robert Fenton, White House monkeypox response coordinator, told reporters.
CBC News has reached out to Health Canada to ask if it is considering reducing dose sizes to stretch its supply of the same vaccine, which goes by the trade name Imvamune in Canada. Just over 1,000 cases of monkeypox have been confirmed in Canada.
Different vaccination technique
The smaller doses also require a different type of injection that penetrates only the top layer of skin, rather than the bottom layer between skin and muscle. This is a less common technique that may require additional training for some health professionals. But infectious disease specialists said that shouldn’t be a major 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 during the 20th century,” said Anne Rimoin, director of the Center for Global and Immigrant Health of the UCLA.
Shallow injection is believed to help stimulate the immune system because the skin contains numerous immune cells that attack foreign invaders.
The CDC said it will provide educational materials on the technique along with a broader awareness campaign for US health departments.
The Biden administration declared monkeypox a public health emergency last week in an effort to curb the outbreak that has infected more than 8,900 Americans.
Officials announced a separate determination Tuesday that allows the Food and Drug Administration to expedite its review of medical products or new uses for them, such as the dose-sparing technique for Jynneos.
The FDA cleared the approach for adults 18 and older who are at high risk for monkeypox infection. Younger people can also get the vaccine if they are considered high risk, though they should get the traditional shot, the agency said.
‘Robust immune response’ to smaller doses
Regulators pointed to a 2015 study showing that inoculation with a fifth of the traditional two-dose vaccine generated a robust immune system response comparable to that of the full dose. About 94 percent of people who received the smaller dose had adequate levels of antibodies against the virus, compared to 98 percent of those who received the full dose, according to the National Institutes of Health-funded study.
The NIH is planning further testing of the technique. Centers for Disease Control and Prevention director Dr. Rochelle Walensky said her agency is already beginning to track the real-world effectiveness of vaccines in US communities, though initial estimates will take time to generate.
But some experts and advocates worried that with little data to back up the policy, it could backfire if it reduces the effectiveness of the vaccine.
“We have serious concerns about the limited amount of research that has been done on this dose and delivery method, and fear that it will give people a false sense of confidence that they are protected,” said David Harvey of the National Coalition for STD directors. , in a sentence.
Vaccine dose rationing 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 uncommon situation,” said Dr. William Moss of the Johns Hopkins Vaccine Access Center. “It all comes down to public health decision-making: In the middle of an outbreak where you don’t have enough supply, do you make this trade-off?”
Both the UK and Canada have adopted a single-dose vaccine strategy that prioritizes people who face the highest risk of monkeypox. And health departments in several large US cities have adopted a similar strategy amid limited supplies, including New York, San Francisco and Washington.
US officials have shipped more than 625,000 full doses of vaccines to state and local health departments. Until now, the vaccines have been recommended for people who have already been exposed to monkeypox or who are likely to get it from recent sexual contact in areas where the virus is spreading.
As of Aug. 8, the Public Health Agency of Canada had shipped more than 85,000 doses of vaccine to provinces and territories, a spokesman said.
CBC News has requested more information about Canada’s vaccine stockpile and its ability to meet demand for immunizations, with some provinces already rationing doses.
Imvamune is usually a two-dose injection, given 28 days apart, with the option of a booster two years later.
But in the guidance for health professionals released in mid juneOntario said it would use a “ring vaccination approach” and offer a single dose in areas with confirmed cases, given the “current limited supply” of vaccines.
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