Who Is Protected Against Monkeypox?

For a world tired of fighting the coronavirus, the monkeypox outbreak poses an important question: Am I at risk?

The answer is reassuring. Most children and adults with healthy immune systems are likely to avoid serious illness, experts said in interviews. But there are two risk groups.

One includes infants under six months of age. But they are not yet affected by the current outbreak. And many older adults, the group most likely to succumb to the monkeypox virus, are at least somewhat protected by decades-old smallpox vaccinations, studies suggest.

Vaccinated older adults can get infected but will likely escape with only mild symptoms.

“The bottom line is that even those vaccinated many decades earlier retain very, very high levels of antibodies and the ability to neutralize the virus,” said Dr. Luigi Ferrucci, scientific director of the National Institute on Aging.

“Even if they were vaccinated 50 years ago, that protection should still be there,” he said.

In the United States, routine smallpox vaccination ceased in 1972. The military continued its vaccination program until 1991 as a precaution against a bioterrorist attack.

Questions about the sustainability of the smallpox vaccine rose after an anthrax attack in 2001, said Dr. Anthony S. Fauci, the Biden administration’s top adviser on infectious diseases. It was reasonable to assume that most vaccinated people were still protected, he said, “but the durability of protection varies from person to person.”

“We cannot guarantee that someone who has been vaccinated against smallpox will still be protected against monkeypox,” said Dr. Fauci.

The monkeypox outbreak has grown to about 260 confirmed cases, with more under investigation in 21 countries.

In the United States, the Centers for Disease Control and Prevention are tracking nine cases in seven states, not all of which have histories of traveling to countries where monkeypox is endemic. That suggests there may already be some degree of community transmission, Dr. Rochelle Walensky, the agency’s director, told reporters on Thursday.

dr. Walensky said 74 labs in 46 states have access to a test that can detect monkeypox, and together they can screen up to 7,000 samples per week. The agency is working to expand that capacity, she said, adding, “We’ve been preparing for these types of outbreaks for decades.”

Monkeypox infection starts with respiratory symptoms but progresses to a distinct rash, first in the mouth, then in the palms and soles, and gradually throughout the rest of the body. The rash eventually becomes raised and grows into pus-filled blisters.

Each pimple contains a live virus, and a ruptured blister can contaminate bedding and other items, putting close contact at risk. Infected people should also be very careful about rubbing their eyes, because the virus can destroy vision

“Before Jenner developed the smallpox vaccine, the leading cause of blindness in the world was smallpox,” said Mark Slifka, an immunologist at Oregon Health and Science University. Infected people are contagious until the pimples crust over and die, he said.

dr. Slifka and other experts stressed that while monkeypox can be serious and even fatal, the current outbreak is unlikely to develop into a major epidemic.

“We’re lucky to have vaccines and therapies — things that can mitigate all of that,” said Anne Rimoin, an epidemiologist at the University of California, Los Angeles, who has studied monkeypox in Africa. “We have the ability to stop this virus.”

Monkeypox takes up to 12 days to cause symptoms, giving doctors a window of at least five days from vaccine exposure and disease prevention. (The approach, called post-exposure prophylaxis, isn’t an option for Covid patients because the coronavirus can devastate the body just days after exposure.)

The monkeypox virus does not spread if there are no symptoms. Close surveillance, isolation of infected people, contact tracing and contact quarantine should contain the outbreak, said Dr. rimoin.

A majority of those currently infected are men under 50, with many identifying as gay or bisexual, which may reflect the possible origin of the outbreak at a Gay Pride event in the Canary Islands. (The outbreak might as well have started among heterosexual people at a major event, experts said.)

“The risk of exposure is not limited to any particular group,” said Dr. Walensky Thursday. “Our priority is to help everyone make informed decisions to protect their health and the health of their communities, and that starts with building awareness, guided by science, not stigma.”

No deaths have been reported. But experts are especially concerned about close contacts that children, older adults or who for other reasons have weak immune systems.

There are conflicting opinions about how long immunity to a smallpox vaccination lasts.

the CDC recommends boosters of smallpox vaccines every three years, but only “for individuals at risk for occupational exposure,” David Daigle, an agency spokesperson, said in a statement.

“Until we know more, we will use available vaccine stocks for people who have had close contact with known cases, and people who are most at risk for exposure through their work, such as health professionals treating monkey pox patients,” he said.

The United States and several European countries have begun immunizing close contacts of infected patients, an approach called ring vaccination.

Many of the most vulnerable groups may already be protected. In one study, Dr. Slifka and his colleagues drew blood from 306 vaccinated volunteers, some of whom had been immunized decades earlier, including one who had been immunized 75 years earlier. Most of them retained high levels of antibodies to smallpox.

In another study, Dr. Slifka and his colleagues suggest that: produced antibodies even a single dose of the smallpox vaccine drops very slowly in the body, by half after about 92 years.

dr. Ferrucci and his colleagues at the NIH, as well as other teams, have also found that antibody levels last for decades after vaccination. Some studies have found that other branches of the immune system also decline slowly, but antibodies produced by smallpox vaccination may be sufficient on its own to protect against monkey pox.

If smallpox started to spread, it would make sense to immunize anyone exposed because of the high death rate, regardless of prior vaccination, said Gigi Gronvall, a biosecurity expert at the Johns Hopkins Center for Health Security.

“We don’t want to risk anyone being left unprotected,” she said.

But that’s not necessary now, she added: “This is monkey pox.”

Laboratory evidence of antibodies does not prove that smallpox vaccination can protect against monkeypox. But to answer that question, study participants would have to be deliberately infected with smallpox or a related virus, a clearly unethical experiment.

For the same reason, newer smallpox vaccines and drugs have only been tested on animals.

Still, one way to study vaccine effectiveness in humans is to gather evidence during an outbreak. The team of dr. Slifka did just that in 2003, when dozens of Americans became infected with monkey pox after being exposed to infected prairie dogs.

The researchers flew to Milwaukee and took blood from 28 people who had been exposed to the infected prairie dogs. Of the eight people who had been previously vaccinated, five developed an average of three pus-filled blisters, compared with an average of 33 in those who had not been vaccinated.

The other three vaccinated persons had no symptoms not at all. “They didn’t even know they were infected,” said Dr. slimka.

Another study of that outbreak found that in a family of three, the previously vaccinated father developed only two monkeypox lesions, compared to 200 in the unvaccinated mother. Their unvaccinated 6-year-old daughter had about 90 lesions and was in a coma for 12 days.

Questions about the durability of vaccine protection against monkeypox have become of particular interest as the number of cases has risen worldwide. Monkeypox resurfaced among people in Nigeria in 2017, and since then there have been about 200 confirmed cases and 500 suspected cases.

The Democratic Republic of the Congo has 58 deaths recorded and nearly 1,300 suspected cases since the beginning of this year.

People in African villages got monkey pox from animals while hunting, but rarely infect others. “It’s only very recently, like the last couple of years, when we started to see this,” said Dr. Rimoin on larger outbreaks.

Smallpox eradication, while one of the greatest public health achievements, has left the population vulnerable to the virus and its cousins.

Declining immunity, coupled with an increase in population and greater proximity to wildlife, may lead to more frequent outbreaks of monkeypox, Dr. Rimoin and her colleagues warned in 2010

Rampant outbreaks, especially among immunocompromised people, would make the virus more likely to acquire mutations that make it more resilient — in humans and animals.

“If monkeypox were to establish itself in a wildlife reservoir outside Africa, the public health setback would be huge,” said Dr. rimoin. “That, I think, is a legitimate concern.”


SOURCE – www.nytimes.com

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