A shortage of monkeypox vaccine doses for monkeys in the United States, expected to last for months, is raising pressing questions about how and how long a single shot can protect against smallpox. virus again.
The vaccine, called Jynneos, is approved as a two-dose regimen, but most people at risk have been given a dose – if they can find one. Now, the shortage has prompted federal officials to consider a rarely used approach: a so-called dose-saving strategy, which provides injections that each contain only a fifth of a single dose. best.
For most recipients, one shot is enough to avoid serious illness, and there is some evidence that smaller doses may also be effective. But preliminary research suggests that people with HIV or other conditions that weaken the immune system may be less protected than people without such conditions, according to some experts.
“A dose is better than nothing,” says Dr. Alexandra Yonts, an infectious disease physician at the National Children’s Hospital in Washington, DC. she added.
Even two weeks after injection, when an antibody response is underway, immunocompromised individuals may still need to “use all other precautions to prevent exposure, according to guidelines public health,” she said.
The findings also suggest that some men should be given priority to be fully vaccinated. With supply constraints, that can be difficult.
Federal officials have ordered nearly seven million doses of Jynneos, but the shots won’t arrive for months. To date, the Biden administration has shipped about 600,000 doses of the drug to the states. Last week it said 800,000 additional doses has been allocated to states, but distribution may take several weeks.
Facing shortages, some cities, including Washington and New York, are limiting second doses to prolong their supply. Officials at the Food and Drug Administration and the CDC disagreed with that strategy, noting that Jynneos approved as a vaccine given in two doses 28 days apart.
But when federal health officials declared a public health emergency on Thursday, FDA commissioner Dr. Robert Califf said the agency was now considering licensing injections containing only 1/5 of the usual dose, instead distributed between skin layers. of below it.
Everything you need to know about Monkey Smallpox Virus
What is monkeypox? Monkeypox is a virus similar to smallpox, but the symptoms are less severe. It was discovered in 1958, after an outbreak of disease in monkeys kept for research. The virus is mainly found 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, overwhelmingly men. same-sex sex. On July 23, World Health Organization declares monkeypox a global health emergency.
The FDA would need to issue Jynneos an emergency use permit for it to be administered this way.
Dose-saving methods have been used when other supplies of vaccines are scarce. But intradermal vaccination requires more skill than is necessary for traditional vaccination methods.
One shot is probably enough to prevent severe symptoms in most people, and a dose-saving strategy can also be effective. But it’s unclear whether a miniaturized regimen would be enough to prevent infection, and if so, how long that immunity might last, federal health officials said.
Dr Emily Erbelding, an infectious disease specialist at the National Institutes of Health who oversees testing of a Covid vaccine for special populations, said: “We’re in an area where there’s no shortage of vaccines. data.
A cited statistic states that this vaccine is 85% effective against smallpox in monkeys. That data is not from Jynneos’ tests, but from a small study in 1988 looked at the incidence of smallpox in monkeys in people who had been vaccinated against smallpox earlier in their lives.
No major clinical trials of Jynneos as a monkeypox vaccine had been conducted in humans prior to approval. Instead, the FDA relied on measurements of antibody responses in a small group of people after vaccination with Jynneos. compared to those produced by ACAM2000an earlier vaccine for smallpox.
In studies by its manufacturer, Bavarian Nordic, two doses of Jynneos yielded human antibody levels comparable to those following a single injection of ACAM2000.
Antibody levels after the first injection of Jynneos initially increased for two weeks and then remained the same until the second dose four weeks later, when they spiked to very high levels – higher than those observed with ACAM2000.
Scientists read that to mean that if the first dose is not followed by a second dose, the protection may not be long-lasting.
Dr Yonts, who reviewed the data for the FDA as a staff scientist, said: “At best, a second dose would be used if protection beyond that 4 weeks is desired. .
She added that delaying the second dose to eight weeks might be reasonable. “But if it lasts like six months, then I think the preference will go to people with more severe immunodeficiency,” she said.
Injections 1/5 of the usual dose of Jynneos between layers of skin, as the FDA suggested on Thursday, may be effective, according to limited research. The skin has more immune cells in response to the vaccine.
But research is very limited. Scientists at the NIH plan to test the dose-saving strategy in a clinical trial that will begin in a few weeks. It is unclear whether those plans will be shelved or accelerated.
Information about how Jynneos performs in people with HIV, especially in those with severe immune problems, has been scant. In a study conducted by Bavarian Nordic, the antibody response to vaccination tend taper off: At 28 days after the first shot, 67% of people with HIV antibody productioncompared with 84 percent of those who were not infected.
While Dr. Yonts said the data from that trial were inconclusive, a reduced antibody response is commonly seen in immunocompromised people receiving other vaccines. For example, while evaluating a Covid vaccine, researchers found that HIV-infected patients were more likely to breakthrough infection.
Keri Althoff, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, who led the Covid vaccine study, said: “It is recommended that people with severe or moderate immunocompromise receive additional treatment. usual vaccine dose. “As immunosuppression increases, the response to the vaccine decreases.”
CDC and New York City Department of Health say Jynneos is safe for people living with HIV, but agencies have not yet addressed its effect on that population.
In contrast, health officials in the UK Speak that for people who “have HIV or have any other condition or treatment that leads to a weakened immune system, the vaccine may not protect you either.”
Types of Vaccines insert package also notes that people who are immunocompromised “may have a reduced immune response.”
Dr Chloe Orkin, an infectious disease physician at Queen Mary University of London, said: “Two shots could be very important in this population, which is something that doesn’t really happen in the public health response. copper.
But until more doses are available, state and local health departments may not have much choice but to adopt miniaturized regimens.
“In an environment of scarcity, we have to do everything we can to get the benefits of the vaccine to the city as quickly as possible,” said Patrick Gallahue, a spokesman for the New York City health department.
