There is a monkeypox vaccine. But not everyone needs it

VShe number of monkeypox continues to rise around the world, raising concerns about how people can protect themselves. So far, the World Health Organization reports that in 12 countries, 92 cases have been confirmed in this recent emergence of the virus, and 28 possible cases are still under investigation. What worries public health officials about recent outbreaks is that monkeypox is not generally common or known to circulate in these countries; it is endemic in parts of central and western Africa, but not in European and North American countries, including the United States, which are currently experiencing an increase in infections. The United States recorded its first case this year in Massachusetts on May 18, and officials from the United States Centers for Disease Control and Prevention (CDC) said at a May 23 briefing that the agency was working with state health departments in New York, Florida, and Utah to investigate four other potential cases.

The good news is that there is already an approved, effective, and relatively new monkeypox vaccine. But should Americans get vaccinated?

monkeypox vaccine

Made by Danish company Bavarian Nordic and named Jynneos, the vaccine uses a live version of the smallpox virus that has been engineered so it cannot replicate in the body or cause infection, but can still activate the immune system. to mount defenses against both the smallpox and monkeypox viruses to protect people from infection. According to studies of vaccinated people in Africa, where the virus has been circulating for years, two doses of the vaccine, given 28 days apart, were up to 85% effective in protecting people against monkeypox. It was approved by the United States Food and Drug Administration (FDA) in 2019 to protect against both smallpox and monkeypox.

Americans are not routinely vaccinated against either disease. But in November 2021, the Advisory Committee on Immunization Practices (ACIP) within the CDC considered who should be vaccinated against monkeypox, as cases in the United States occurred after people traveled to areas of Africa where the disease is endemic. After reviewing available studies, ACIP recommended that those most at risk of exposure and infection, including scientists who work in laboratories that study monkeypox virus, first responders likely to treat these professional cases and healthcare workers caring for infected patients. receive the vaccine. The recommendations were accepted by CDC Director Dr. Rochelle Walensky, but were not published in the agency’s official publication, the MMWRwhich would formalize the notice.

“ACIP has done a very good job of considering all the different populations that might have occupational exposure risks. [to monkeypox]says Brett Peterson, deputy chief of the CDC’s smallpox virus and rabies branch. But, he says, that was before the current clusters of cases, and committee members focused primarily on how best to protect those at high occupational risk from infection, as there were no significant risk of cases in the general population. In view of the latest developments, this recommendation may be modified before publication to provide additional guidance on the best strategy to vaccinate other people who may be exposed if more cases appear.

“There is probably a need to call on the CDC to release decisions made by ACIP regarding the use of the monkeypox vaccine, given recent cases,” says Dr. David Freedman, professor emeritus of infectious diseases at the University of Alabama at Birmingham. and president-elect of the American Society of Tropical Medicine and Hygiene.

A possible vaccine approach

Unlike COVID-19 vaccines, vaccinating people against monkeypox is unlikely to involve a mass campaign, because monkeypox is not as contagious or as easily spread as SARS-CoV-2. Monkeypox was discovered in 1958 and named after colonies of monkeys, which were part of research studies, in which the virus was first identified. In recent years, human cases have been reported mainly in central and western African countries such as Nigeria and Cameroon, with the West African virus, which circulates widely in Nigeria, causing less severe disease than the Central African version. As a poxvirus, its symptoms are similar to those of smallpox and include fever, muscle aches and headaches. Unlike smallpox, however, monkeypox also causes the lymph nodes to swell and, several days after the initial fever, characteristic lesions begin to appear throughout the body, eventually developing into larger fluid-filled blisters and pustules. before forming scabs. Most people with the disease recover without treatment after two to four weeks, although antiviral therapies can be helpful, especially for people with weakened immune systems. During the May 23 press briefing, CDC scientists noted that data showing the effectiveness of these antiviral treatments in human patients is still limited and that most of the data supporting their use comes from studies. animal.

The virus can be spread by a number of routes, the most common and direct being through breaks in the skin or through contact with bodily fluids. Monkeypox and is also spread from person to person through respiratory droplets from sneezes or saliva, although infection is less likely to occur this way and more likely to occur through direct contact with loaded lesions of viruses.

This is why the monkeypox vaccination will most likely involve some version of what experts call a ring strategy and will focus on immunizing only people in contact with infected people. “If a case is reported in the country, a public health SWAT team goes there, finds out who the close contacts of this first case are and vaccinates only those close contacts, not the whole city or suburb,” explains Freeman. “Because monkeypox is not a virus that is spread primarily through the respiratory route, you don’t see a large number of infected people. So you can do a ring vaccination around known cases.

If this approach is used, “we have enough vaccine in the strategic national stockpile to vaccinate the entire US population,” Peterson says. “I am confident that there are enough vaccines available to be used in this situation.” The United States’ initial contract with Bavarian Nordic after the vaccine was approved called for the supply of 28 million doses of vaccine for the stockpile over several years. But because some of those doses were delivered around 2019, some expired, and the terms of the deal require the company to replace expired doses with freshly made ones.

Capt. Jennifer McQuiston, deputy director of the CDC’s division of high-consequence pathogens and pathology, told the press conference that approximately 1,000 doses of the vaccine are currently available and that Bavarian Nordic plans to increase production to increase this supply. Additionally, on May 18, the U.S. Biomedical Advanced Research and Development Authority (BARDA), part of the Department of Health and Human Services, called in an existing order for up to 13 million additional frozen doses. to add to this inventory. The currently stocked versions of the vaccine were made in liquid form and then frozen, giving them a shorter shelf life, according to Peterson. The new freeze-dried versions are first turned into a powder which makes them more resistant to temperature changes before being reconstituted just before being injected. But these more stable vaccines won’t be available until 2023 and 2024.

McQuiston added that so far, Massachusetts Department of Health officials have identified more than 200 close contacts of the single confirmed case of monkeypox in the United States — most of whom are health care workers — and that some of those contacts were vaccinated with doses from the national stock.

This stockpile also contains doses of a different, older smallpox vaccine, which has not been reviewed or approved by the FDA specifically for monkeypox, but could also be used to protect people against the latter disease, since the viruses are linked and the injections can generate immunity that can cross-react with both viruses. This vaccine, called ACAM2000, has been approved in the United States, Australia and Singapore to protect against smallpox, but can cause side effects, including inflammation of heart tissue, and is not recommended for people with immune system is weakened. Unlike Jynneos, ACAM2000 is built around a disabled monkeypox virus that is still able to replicate, although it cannot cause disease. Jynneos was developed specifically to offer people with weakened immune systems an option to get vaccinated against smallpox, but its safer profile led the FDA to approve it for the general population as well. The ability of the vaccine to cross-react and generate immune protection against monkeypox made it doubly useful. “It’s important to know that Jynneos can be given to people without the need for a detailed medical examination,” Freedman says.

There’s not yet strong enough evidence to suggest where and how the recent outbreaks started, but the clusters in Europe involve men who have sex with men, and “many of these global case reports of monkeypox are occur within sexual networks,” CDC poxvirus expert Dr. Inger Damon said in a statement posted on the agency’s website.

The first genetic analysis of monkeypox viruses from recent cases suggests they originated in Nigeria, where one of two common versions of the virus is endemic, and were brought to other parts of the world via infected travellers. But researchers will continue to further analyze the genetic data to understand if and how the latest clusters of cases are related.

In the meantime, should the outbreak grow large and wide enough to warrant vaccination, health experts in the United States are confident that there will be enough doses of vaccine to distribute to Americans who may need.

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