Explainer: what vaccines, treatments do we have to fight monkey pox?

With cases of monkeypox inexplicably increasing outside of Africa — where the viral disease is endemic — public health officials are using contact tracing, isolation and targeted vaccination to curb its spread.

Global health officials have monitored more than 200 suspected and confirmed cases of the usually mild viral infection in 19 countries since early May. The monkeypox variant implicated in the current outbreak has a fatality rate of about 1%, although no deaths have been reported so far.

Here’s what we know about the existing range of vaccines and treatments:

Vaccines

The smallpox and monkeypoxviruses are closely related, and first-generation smallpox vaccines have been shown to be up to 85% effective in preventing monkeypox, according to the World Health Organization.

There are currently two smallpox vaccines available.

One made by the Danish company Bavarian Nordic bears the brand name Jynneos, Imvamune or Imvanex – depending on the geography.

It contains an attenuated form of the vaccinia virus that is closely related to, but less harmful than, the viruses that cause smallpox and monkeypox. This modified version of vaccinia does not cause disease in humans and cannot reproduce in human cells.

It has US approval for the prevention of both smallpox and monkeypox. The European Union approval is for smallpox, although doctors can prescribe it off-label for monkeypox. Bavarian Nordic said it would likely request a label extension from the EU drug watchdog to include monkeypox.

The side effects reported are pain and swelling at the injection site, as well as headache and fatigue.

The other, older vaccine, currently made by Emergent Biosolutions, is called ACAM2000.

It also contains the vaccinia virus, but it is contagious and can multiply in humans. As a result, it can be transmitted from the vaccine recipient to unvaccinated people who have close contact with the vaccination site.

Aside from the side effects associated with many vaccines, such as arm sore and fatigue, it also carries a serious warning sign of a potential range of serious complications, including heart inflammation, blindness and death.

It is also not designed for use in certain groups of people, such as those with compromised immune systems.

ACAM2000 has US approval for people at high risk of smallpox infection. It does not have an EU license.

Antivirals

Monkeypox symptoms — including fever, headache, characteristic rash, and pus-filled skin lesions — can last for two to four weeks and often go away on their own.

Patients may receive additional fluids and treatment for secondary bacterial infections. An antiviral called tecovirimat — branded as TPOXX and made by SIGA Technologies — has US and EU approval for smallpox, while European approval also includes monkeypox and cowpox.

Another drug, branded as Tembexa and developed by Chimerix, has US approval to treat smallpox. It’s not clear if it can help people infected with monkey pox.

Both TPOXX and Tembexa have been approved based on animal studies showing that they are likely to be effective, as they were developed after smallpox was eradicated from humans through mass vaccination.

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The WHO classified smallpox as an eradicated disease in 1980, but there has long been concern that the virus could be used as a bioweapon, leading countries to develop vaccines.

The WHO has 2.4 million doses in its Swiss headquarters dating back to the final years of its eradication program. The agency also has pledges from donor countries for more than 31 million additional doses.

US officials say there are more than 1,000 doses of the Bavarian Nordic vaccine in the national supply and expect that level to rise very quickly in the coming weeks. The country also has 100 million doses of ACAM2000.

Germany has said it has ordered 40,000 doses of the Bavarian Nordic vaccine, to be ready to vaccinate contacts of cases if necessary.

Other countries, including Britain and France, also offer or recommend vaccines to people who have close contact with infected people and health professionals.

Bavarian Nordic, which has an annual production capacity of 30 million doses, told Reuters that multiple countries have approached the company interested in buying its vaccine, without providing details. A spokesperson said there is no need to expand production.