For a world tired of fighting the coronavirus, the monkeypox epidemic raises a key question: Am I at risk?
The answer is reassuring. Most children and adults with a healthy immune system are likely to avoid serious illness, experts said in interviews. But there are two high-risk groups.
One includes babies under six months. But they are not yet affected by the current epidemic. And many older people, the group most likely to succumb to the monkeypox virus, are at least somewhat protected from decades of smallpox vaccinations, studies show.
Vaccinated adults can become infected, but are likely to escape with only mild symptoms.
“The bottom line is that even those who have been vaccinated many decades before maintain very, very high levels of antibodies and the ability to neutralize the virus,” said Dr. Luigi Ferrucci, research director at the National Institute on Aging.
“Even if they were vaccinated 50 years ago, this protection still needs to be in place,” he said.
In the United States, routine smallpox immunization was discontinued in 1972. The military continued its vaccination program until 1991 as a precaution against a bioterrorism attack.
Questions about the durability of the smallpox vaccine have risen since an anthrax attack in 2001, said Dr. Anthony C. Fauci, chief adviser to the Biden administration on infectious diseases. It is reasonable to assume that most vaccinated people are still protected, he said, “but the durability of protection varies from person to person.”
“We cannot guarantee that a person who has been vaccinated against smallpox will still be protected against monkeypox,” said Dr Fauci.
The outbreak of monkeypox has risen to about 260 confirmed cases and dozens more are being investigated in 21 countries.
In the United States, the Centers for Disease Control and Prevention is tracking nine cases in seven states, not all of which have traveled to countries where monkeypox is endemic. This suggests that there may already be some level of transmission in the community, Dr Rochelle Valenski, the agency’s director, told reporters on Thursday.
Dr Valenski said 74 laboratories in 46 states have access to a test that can detect monkeypox, and together they can test up to 7,000 samples a week. The agency is working to expand that capacity, she said, adding: “We have been preparing for this type of outbreak for decades.
The monkeypox infection begins with respiratory symptoms, but blooms in a distinct rash, first in the mouth, then on the palms of the hands and feet, and gradually on the rest of the body. The rash eventually rises, growing into pus-filled blisters.
Each pustule contains a live virus, and a leaking blister can contaminate bedding and other items, putting close contact at risk. Infected people should also be careful to rub their eyes, because the virus can destroy vision.
“Before Jenner developed the smallpox vaccine, the number one cause of blindness in the world was smallpox,” said Mark Slifka, an immunologist at the University of Oregon Health and Science. Infected people are contagious until the pustules are covered and excreted, he said.
Dr. Slifka and other experts point out that while smallpox can be severe and even fatal, the current outbreak is unlikely to escalate into a major epidemic.
“We’re lucky to have vaccines and therapies – things that can alleviate all this,” said Anne Remoin, an epidemiologist at the University of California, Los Angeles who studied monkeypox in Africa. “We have the ability to stop this virus.”
Monkeypox takes up to 12 days to cause symptoms, which gives doctors a window of at least five days after exposure to vaccination and prevention of the disease. (An approach called post-exposure prophylaxis is not an option for Covid patients because the coronavirus can begin to devastate the body just days after exposure.)
The monkeypox virus does not spread in the absence of symptoms. Careful monitoring, isolation of infected people, tracking of contacts and quarantine of contacts should control the outbreak, said Dr. Rimoin.
The majority of those infected are now under the age of 50 and many identify as gay or bisexual, which may reflect the possible origins of the epidemic during a gay pride event in the Canary Islands. (The outbreak could just as easily start among heterosexuals at a major event, experts said.)
“The risk of exposure is not limited to any particular group,” Dr Valenski said on Thursday. “Our priority is to help everyone make informed decisions to protect their health and the health of their community, and that starts with building awareness, driven by science, not stigma.
There are no reports of deaths. But experts are particularly concerned about close contacts who are children, the elderly or who have a weak immune system for other reasons.
There are conflicting opinions about how long immunity from smallpox vaccination lasts.
The CDC recommends booster vaccines against smallpox every three years, but only “for people at risk of occupational exposure,” said David Digel, a spokesman for the agency.
“Until we find out more, we will use the available stockpiles of vaccines for people who have had close contact with known cases and people at highest risk of exposure through their work, such as health workers treating monkeypox patients,” he said. .
The United States and several European countries have begun to immunize 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 colleagues took blood from 306 vaccinated volunteers, some of whom had been immunized decades earlier, including one immunized 75 years ago. Most of them maintain high levels of antibodies against smallpox.
In another study, Dr. Slifka and colleagues showed that antibodies produced by even a single dose of the smallpox vaccine declined very slowly in the body, halving after about 92 years.
Dr. Ferrucci and his colleagues at the NIH, as well as other teams, also found that antibody levels persisted for decades after vaccination. Some studies have found that other branches of the immune system also weaken slowly, but antibodies produced by smallpox vaccination may be enough on their own to protect against monkeypox.
If smallpox begins to spread, it would make sense to immunize anyone who is exposed to high mortality, regardless of previous vaccinations, said Gigi Gronval, a biosafety expert at the Johns Hopkins Center for Health Security.
What you need to know about the monkeypox virus
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What is monkeypox? Monkeypox is a virus endemic to parts of Central and West Africa. It is similar to smallpox, but less severe. It was discovered in 1958 after outbreaks in monkeys kept for testing, according to the Centers for Disease Control and Prevention.
What are the symptoms? Monkeypox creates a rash that begins with flat red spots that rise and fill with pus. Infected people may also have fever and body aches. Symptoms usually appear within six to 13 days, but it can take up to three weeks after exposure for them to appear and can last for two to four weeks. Health officials say smallpox vaccines and other treatments can be used to control the outbreak.
How contagious is it? The virus is spread through body fluids, skin contact and respiratory droplets. This does not usually lead to large outbreaks, although it has spread in unusual ways this year and among populations that have not been vulnerable in the past.
Should I be worried? The virus is more likely to spread during sexual intercourse, but the risk of transmission in other ways is low. Most people have mild symptoms and recover within weeks, but the virus can be fatal in a small percentage of cases.
“We don’t want to risk leaving someone unprotected,” she said.
But that’s not necessary now, she added: “It’s monkeypox.”
Laboratory evidence of antibodies does not show that smallpox vaccination can protect against monkeypox. But the answer to this question would require that study participants be intentionally infected with smallpox or a related virus, an apparently unethical experiment.
For the same reason, newer measles vaccines and drugs have only been tested on animals.
Still, one way to study the effectiveness of the vaccine in humans is to gather evidence during an epidemic. Dr. Slifka’s team did just that in 2003, when dozens of Americans became infected with monkeypox after being exposed to infected prairie dogs.
The researchers flew to Milwaukee and took blood from 28 people who were exposed to infected prairie dogs. Of the eight people who had previously been vaccinated, five had developed an average of three pus-filled blisters, compared with an average of 33 who had not been vaccinated.
The other three vaccinated individuals had no symptoms. “They didn’t even know they were infected,” said Dr. Slifka.
Another study of this outbreak found that in a family of three, a previously vaccinated father developed only two monkeypox lesions, compared with 200 in an unvaccinated mother. Their unvaccinated 6-year-old daughter had about 90 lesions and was in a coma for 12 days.
Questions about the longevity of monkey vaccination protection have become particularly important as the number of cases worldwide has increased. Monkeypox reappeared among people in Nigeria in 2017, and there have been about 200 confirmed cases and 500 suspected cases since then.
The Democratic Republic of the Congo has registered 58 deaths and nearly 1,300 suspicious cases since the beginning of this year.
People in African villages became infected with monkeypox while hunting, but rarely infected others. “Only recently, in the last few years, have we begun to see this,” Dr. Remoin said of the larger outbreaks.
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