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 limit its spread.
Global health officials have tracked more than 200 suspected and confirmed cases of usually mild viral infection in 19 countries since early May. The monkeypox variant implicated in the current outbreak has a case fatality rate of about 1 percent, although no deaths have been reported so far.
Here’s what we know about the current range of vaccines and treatments:
The World Health Organization has said that the smallpox and monkeypox viruses are closely related, and first-generation smallpox vaccines appear to be up to 85 percent effective in preventing monkeypox.
There are currently two smallpox vaccines.
One made by the Danish Bavarian Nordic company bears the trade name Jynneos, Imvamune or Imvanex – depending on geography.
It contains a weakened form of the vaccinia virus that is closely related to the viruses that cause smallpox and monkeypox, but is less harmful than it. This modified version of the vaccine does not cause disease in humans and cannot replicate in human cells.
It has received US approval for the prevention of both smallpox and monkeys. EU approval is for smallpox, although doctors can prescribe it off-label for monkeypox. The northern state of Bavaria said it would likely file an application for an extension of the designation with the European Union’s drug control body to include monkeypox.
Reported side effects include pain and swelling at the injection site as well as headache and fatigue.
Another 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 vaccine recipients to unvaccinated people who have close contact with the vaccination site.
Aside from the side effects associated with many vaccines, such as arm inflammation and fatigue, it also carries a serious warning for 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 weakened immune systems.
ACAM2000 has been approved by the United States for people at risk of developing smallpox. It does not have permission from the European Union.
Symptoms of monkeypox — which can include fever, headache, a characteristic rash, and pus-filled skin lesions — can last for two to four weeks and often resolve on their own.
Patients may receive additional fluids and treatment for secondary bacterial infections. An antiviral agent called tecovirimat — branded TPOXX and manufactured by SIGA Technologies — has US and EU approval for smallpox, while European approval also includes monkeypox and cowpox.
Another drug, Tembexa and developed by Chimerix, has been approved in the United States to treat smallpox. It’s not clear if it can help people with monkeypox.
Both TPOXX and Tembexa were approved based on animal studies that showed they were likely to be effective, because they were developed after smallpox was eradicated in humans through mass vaccination.
The World Health Organization classified smallpox as an eradicated disease in 1980, but there have been long-standing concerns that the virus could be used as a biological weapon, leading countries to stockpile vaccines.
WHO maintains 2.4 million doses at its headquarters in Switzerland dating back to the last years of the eradication programme. The agency also pledged more than 31 million additional doses from donor countries.
US officials say there are more than 1,000 doses of the North Bavarian vaccine in the national stockpile, and they expect that level to rise very quickly in the coming weeks. The country also has 100 million doses of ACAM2000.
Germany said it had ordered 40,000 doses of the Bavaria-Scandinavian vaccine, to be ready to vaccinate contacts of the cases if necessary.
Other countries, including Britain and France, are also providing or recommending vaccines for people who are in close contact with infected people and health care workers.
The Bavarian North region, which has an annual production capacity of 30 million doses, told Reuters that several countries had contacted it to purchase its vaccine, without providing details. A company spokesperson said it did not need to expand production.
(Reporting by Natalie Grover in London, Twitter by NatalieGrover; Additional reporting by Nikolai Skidsgaard in Copenhagen and Michael Ehrman in New Jersey; Editing by Michael Gershberg, Josephine Mason and Jane Merriman)