June 1, 2023

Monkey pox: how the vaccine works

FOCUS – As the monkeypox epidemic spreads around the world, a third generation vaccine is recommended for contact cases.

In France, there are currently 16 confirmed cases of monkeypox. Outside Africa, where the virus is endemic, the toll stands at nearly 300 cases recorded in 20 countries. As a reminder, monkey pox, a disease related to smallpox, eradicated for about forty years, is caught after prolonged contact with a patient, in particular by the exchange of biological fluids. In order to stop its progression, the Haute Autorité de Santé, in a report published on May 24, positioned itself in favor of a “active vaccination strategy“.

However, there is no specific vaccine for monkeypox, which is fatal in 3 to 6% of cases. But smallpox vaccines are, according to several studies, 85% effective. This vaccine, called Imvanex and manufactured by the Bavarian Nordic laboratory, works on the principle of an injection of a live modified form of the virus, called here “vaccine Ankara”, which does not present a risk for humans. Thus, the immune system prepares antibodies to fight the virus.

According to the HAS, anyone presenting themselves as a contact at risk should be vaccinated within four days, before a second dose 28 days after the first. For immunocompromised people, a third dose should be injected again 28 days later.

SEE ALSO – “There is no specific treatment for monkeypox”, explains Marc Cherki

More than 70 million doses ahead

France would have a stock of more than 70 million doses in advance, according to a 2006 document from the Ministry of Health, called the National Smallpox Threat Response Plan. Brigitte Bourguignon, the new health minister, said that “stocks are perfect for now“.

However, according to the document, these would be second-generation vaccines, as used in the 1970s and 1980s. These worked quite well and led to the eradication of smallpox in 1984, but presented ‘significant side effects, such as heart damage and encephalopathy, so they were contraindicated for pregnant women and immunocompromised people.

Minimal side effects

Regarding the Imvanex vaccine, its side effects are minimal: simple redness or slight swelling around the injection site. The European Union is preparing group purchases of vaccines and other treatments against monkeypox, the European Commission said on Thursday (26 May).

The WHO, however, indicated on Friday that a general vaccination of the population was not planned and that the isolation of the sick remained the first weapon against the epidemic.

SEE ALSO – Monkey pox: Brigitte Bourguignon wants to “eradicate the problem” thanks to European cooperation


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