Monkeypox cases are being identified in several countries around the world where the rare disease is not normally found, including the United States, raising questions about the availability of vaccines for the disease.
During May, more than 100 cases of monkeypox were identified outside of central and west Africa, where the disease caused by the monkeypox virus is endemic, with several other suspected cases reported.
The majority of cases recently identified in non-endemic countries have occurred in Europe – mainly in Portugal, Spain and the UK. Meanwhile, the United States and Canada have confirmed two and five cases, respectively.
Investigations into the latest cluster are ongoing, 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?
Although there’s no specific, widely used vaccine for monkeypox itself, experts say shots could be used to prevent smallpox — a related virus — to control an outbreak if needed.
“The viruses that cause smallpox and monkeypox are from the same family and are quite similar biologically,” said Daniel Bausch, president of the American Society of Tropical Medicine and Hygiene news week.
“Smallpox was declared eradicated in 1980, and monkeypox is a relatively rare disease that occurs sporadically in Africa, so there hasn’t been much effort to develop new smallpox or monkeypox vaccines in the past,” he said. “However, this changed after the 2001 anthrax attacks in the United States, which increased concerns about bioterrorism.”
While the original smallpox vaccine that helped eradicate the disease is no longer available, after the anthrax attacks, a new smallpox vaccine (called Jynneos in the US, also known as Imvamune or Imvanex in other regions) was developed and approved in the United States States and Canada for the prevention of smallpox, with approval extended to include monkeypox.
The vaccine was also only approved in Europe for the prevention of smallpox, although it had previously been used off-label in response to cases of monkeypox.
Effective vaccine
Scientists have shown this vaccine to be effective in animal studies and safe in human studies. It contains a virus called vaccinia, in the same family as monkeypox and smallpox, which is generally harmless to humans but can elicit a protective immune response against the group’s more dangerous viruses.
“Not surprisingly, animal studies suggest that the smallpox vaccine provides good protection against monkeypox, probably at least 85 percent,” Bausch said. “Note that while the safety of these vaccines has been demonstrated in humans, Phase III human studies to confirm the results in animals have not been conducted.”
“Such studies would be difficult to conduct given that even in areas where it is endemic in Africa, monkeypox is still a relatively rare disease and is often found in remote areas with inadequate infrastructure,” he said. “But even without Phase III data, I believe there is high confidence that existing smallpox vaccines are safe and effective against monkeypox.”
However, Bausch said this vaccine is not widely available on the open market or to the general public.
“The United States has stocks of it and countries would have to work out agreements with them,” he said. “At this point it would only be indicated for high-risk contacts, including medical workers who have not taken proper precautions. The vaccine is not recommended for the general public.”
Major US government order
Last week, the US government ordered millions of doses of the Jynneos vaccine from manufacturer Bavarian Nordic after a case of monkeypox was confirmed in the country. The first cans of this order are scheduled to be manufactured next year.
The United States also previously approved another smallpox vaccine (dubbed ACAM2000) that the Centers for Disease Control and Prevention says can be used in people who have been exposed to monkeypox under certain protocols. Experts believe that vaccination after exposure to the monkeypox virus could help prevent or reduce the severity of the disease.
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 vaccine several decades ago already have some cross-protective immunity. However, this is limited to people over 40 or 50 years of age.
Despite the small but rising number of monkeypox cases in non-endemic countries, Bausch said the United States doesn’t need mass vaccination programs to control an outbreak.
“The vaccine could be – and in some places already is – an important tool to protect people who have been directly exposed and to curb transmission in these relatively defined populations, but there will be no need for widespread vaccination, and the general public should not panic about this either,” he said.
“This is an event that we need to get to the bottom of, better understand what is happening and of course take action to limit the spread, but monkeypox is not the next COVID-19.”
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