A shortage of monkeypox vaccine doses in the United States, which is expected to last for months, raises urgent questions about how well and for how long a shot can protect against the virus.
The vaccine, called Jynneos, is approved as a two-dose schedule, but most people at risk of infection get one dose — if they can find it. Now, the shortage has prompted federal officials to consider a rarely used approach: the so-called dose-sparing strategy, which gives injections that each contain only one-fifth of a single dose.
For most recipients, one injection should be enough to prevent serious illness, and there is some evidence that even smaller doses can be effective. But preliminary research suggests that people with HIV or other diseases that weaken the immune system may be less protected than people without such diseases, according to some experts.
“One dose is better than none,” said Dr. Alexandra Younts, an infectious disease physician at Children’s Nationwide Hospital in Washington, DC. But people with “HIV and other immunocompromised individuals should be aware that they may not have an adequate level of protection against infection, even with vaccination,” she added.
Even two weeks after the injection, when the antibody response is underway, immunocompromised people may still need to “use all other precautions to prevent exposure, according to public health guidelines,” she said.
The findings also suggest that some men should be prioritized for full vaccination. Given supply constraints, this may be difficult.
Federal officials have ordered nearly seven million doses of Jynneos, but the shots won’t arrive for months. So far, the Biden administration has sent about 600,000 doses to states. It said last week that 800,000 extra doses were being distributed to states, but distribution could take weeks.
Faced with shortages, some cities, including Washington and New York, are limiting second doses to stretch their supplies. Officials from the Food and Drug Administration and the CDC disagree with that strategy, noting that Jynneos is approved as a vaccine to be given in two doses separated by 28 days.
But after federal health officials declared a public health emergency on Thursday, Dr. Robert Califf, the FDA commissioner, said the agency is considering allowing injections that contain just one-fifth of the usual dose to be delivered between the layers instead of the skin beneath it.
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.
What is the treatment for monkeypox? If you do get sick, treating monkeypox usually involves controlling the symptoms. Tecovirimat, an antiviral drug also known as TPOXX, can sometimes be used in severe cases. The Jynneos vaccine, which protects against variola and monkeypox, can also help reduce symptoms, even if taken after exposure.
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.
The FDA would need to grant Jynneos emergency use authorization to be administered this way.
The dose-saving approach has been used when supplies of other vaccines are scarce. But giving intradermal injections requires more skill than more traditional immunizations.
One injection is probably enough to prevent severe symptoms in most people, and a dose-saving strategy may work just as well. But it’s unclear whether the reduced regimen is enough to prevent infection, and if so, how long that immunity might last, federal health officials said.
“We’re in a no-data zone,” said Dr. Emily Erbelding, an infectious disease expert at the National Institutes of Health who led testing of Covid vaccines in special populations.
One oft-quoted statistic says that the vaccine is 85 percent effective against monkeypox. These data did not come from trials with Jynneos, but from a small study from 1988 that looked at the incidence of monkeypox among people who had been vaccinated against smallpox earlier in life.
There was no large clinical trial of Jynneos as a monkeypox vaccine in humans before its approval. Instead, the FDA relied on measures of antibody responses in small groups of people after immunization with Jynneos compared to those produced by ACAM2000, an earlier smallpox vaccine.
In studies led by its manufacturer, Bavarian Nordic, two doses of Jynneos produced antibody levels in humans that were almost the same as those after a single injection of ACAM2000.
Antibody levels after the first dose of Jynneos initially rose for two weeks and then remained unchanged until the second dose four weeks later, when they jumped to very high levels – higher than those recorded with ACAM2000.
Scientists read that if the first dose is not followed by a second, the protection may not be long-lasting.
“Ideally, a second dose would be administered if protection for more than that four-week period is desired,” said Dr. Younts, who reviewed the data for the FDA as a staff scientist.
She added that delaying the second dose until eight weeks might be reasonable. “But if it’s going to be about six months, then I think the prioritization will lean more toward those who are more severely immunocompromised,” she said.
Injecting one-fifth of the regular dose of Jynneos between the layers of the skin, as the FDA suggested Thursday, may be effective, according to limited research. The skin has many more immune cells that respond to vaccines.
But research is very limited. The NIH scientists planned to test the dose-saving strategy in a clinical trial that was set to begin in a few weeks. It is unclear whether those plans will be delayed or accelerated.
Information about how Jynneos works in people with HIV, especially those with severe immune problems, was already scarce. In a study conducted by Bavarian Nordic, the antibody response to vaccination tended to be reduced: 28 days after the first vaccine, 67 percent of people with HIV produced antibodies, compared to 84 percent of uninfected people.
Although Dr. Yonts said the data from this trial were inconclusive, a reduced antibody response is often seen among immunocompromised people who have been given other vaccines. While evaluating Covid vaccines, for example, researchers found that HIV patients were more likely to have breakthrough infections.
“For people with severe or moderate immune suppression, additional doses of the usual vaccines are recommended,” said Kerry Althoff, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health who is leading the Covid vaccine study. “As immune suppression increases, the response to vaccines does decrease.”
The CDC and the New York City Department of Health say Jynneos is safe for people with HIV, but the agencies have not looked at its effectiveness in this population.
Conversely, health authorities in Britain say that for people who “are HIV positive or have any other disease or treatment that results in a weakened immune system, the vaccine may not protect you as well”.
The vaccine leaflet also notes that immunocompromised people “may have a weakened immune response”.
“Two shots may be very important for this population, which is not really happening in the public health response,” said Dr. Chloe Orkin, an infectious disease physician at Queen Mary University of London, referring to immunocompromised people.
But until more doses are available, state and local health departments may have little choice but to stick with reduced regimens.
“In an environment of shortages, we need to do everything we can to get the benefits of the vaccine to the city as quickly as possible,” Patrick Gallahue, a spokesman for the New York City Department of Health, said in a statement.
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