Can You Get Vaccinated for Monkeypox?

Monkeypox cases are being identified in several countries around the world where the rare disease isn't usually found, including in the United States, prompting questions about the availability of vaccines for the disease.

Over the course of May, more than 100 monkeypox cases have been identified outside Central and West Africa where the disease—caused by the monkeypox virus—is endemic, with several more suspected cases reported.

The majority of the recent cases identified in non-endemic countries have occurred in Europe—mostly in Portugal, Spain and the United Kingdom. Meanwhile, the United States and Canada have confirmed two and five cases, respectively.

Investigations are ongoing into the recent cluster, with the World Health Organization describing the identification of cases with no established travel links to endemic areas as "highly unusual."

Can You Get Vaccinated?

While there is no specific, widely available vaccine for monkeypox itself, shots designed to prevent smallpox—a related virus—could be used to control an outbreak if necessary, according to experts.

"The viruses that cause smallpox and monkeypox come from the same family and are quite similar biologically, Daniel Bausch, president of the American Society of Tropical Medicine and Hygiene, told Newsweek.

"Smallpox was declared eradicated in 1980 and monkeypox is a relatively rare disease seen only sporadically in Africa, so historically there has not been a big drive to develop new smallpox or monkeypox vaccines," he said. "However, this changed in the wake of the 2001 anthrax attacks in the United States, which heightened concern over bioterrorism."

While the original smallpox vaccine, which helped to eradicated the disease, is no longer available, a new smallpox vaccine (called Jynneos in the U.S., but also known as Imvamune or Imvanex in other regions) was developed following the anthrax attacks and has been licensed in the United States and Canada to prevent smallpox with approval extended to cover monkeypox.

The vaccine has also been approved in Europe for the prevention of smallpox only, although it has previously been used off-label in response to monkeypox cases.

Effective Vaccine

Scientists have shown that this vaccine is effective in animal studies and safe in human studies. It contains a virus called vaccinia from the same family as monkeypox and smallpox that is generally harmless to humans, but which can induce a protective immune response to the more dangerous viruses in the group.

"Not surprisingly, studies in animals have suggested that the smallpox vaccine affords good protection against monkeypox, probably at least 85 percent," Bausch said. "Note that, although safety of these vaccines has been established in humans, Phase III studies in humans to confirm the findings from animals have not been done."

"Such studies would be difficult to do considering that monkeypox is still a relatively rare disease even in the areas where it is endemic in Africa, and often found in remote areas with insufficient infrastructure," he said. "But even in the absence of Phase III data, I think there is a lot of confidence that existing smallpox vaccines are safe and effective for monkeypox."

Bausch said, however, that this vaccine isn't widely available, either on the open market or to the general public.

"The United States has stockpiles of it and countries would need to work out arrangements with them," he said. "At this point it would only be indicated for high-risk contacts, including health care workers who did not take appropriate precautions. The vaccine is not recommended for the general public."

Big U.S. Government Order

Last week, the U.S. government ordered millions of doses of the Jynneos vaccine from the manufacturer Bavarian Nordic following confirmation of a monkeypox case in the country. The first doses of this order are expected to be manufactured next year.

The United States has also previously authorized another smallpox vaccine (called ACAM2000) that can be used in people who have been exposed to monkeypox under certain protocols, according to the Centers for Disease Control and Prevention. Experts think that vaccination after exposure to the monkeypox virus could help to prevent the disease or reduce its severity.

The United States also has stockpiles of this vaccine in case it's ever needed, but, like Jynneos, the shot isn't available to the general public.

Some older people who received the smallpox vaccination several decades ago will already have some cross-protective immunity. But this is limited to people over the age of 40 or 50.

Despite the small but increasing number of recent monkeypox cases in non-endemic countries, Bausch said that mass vaccination programs won't be needed in the United States to control any outbreak.

"Vaccine might—and already is in some places—be an important tool to protect people who have been directly exposed and to stem transmission in these relatively defined populations, but there will not be a need for widespread vaccination, and the general public should not be panicking about this," he said.

"This is an event which we need to get to the bottom of, better understand what's happening, and of course take steps to limit spread, but monkeypox is not the next COVID-19."

A medical syringe and vaccine
A file photo of a vaccine and a syringe. Smallpox vaccines are thought to provide some protection against monkeypox. iStock