The epidemic continues to spread: more than 300 cases of monkeypox have been confirmed as of May 27 in nearly twenty countries outside the African continent, where the disease is endemic in about ten countries. An extraordinary dispersion which has prompted many countries to brandish the vaccine weapon in an attempt to stem the disease before it takes on too large proportions. To stifle this outbreak, the High Authority for Health (HAS) thus recommends, in its opinion of May 24, to vaccinate all individuals who have been in contact with a confirmed case, as well as all people in contact with this first circle. This is the “ring vaccination” strategy, which had proved its worth in particular against the last smallpox epidemics.
There is no specific vaccine against monkeypox, but studies have shown that smallpox vaccination is about 85% effective against monkeypox and helps reduce symptoms. World Health Organization. “The reason is clear: all these viruses belong to the same small family called orthopoxvirus and there is a wide cross-immunity,” explains David Freedman, president of the American Society of Tropical Medicine and Hygiene. The vaccine against smallpox is also based on the cowpox virus, a cousin of this same family which went down in history by giving its name to vaccination.
Very attenuated strain
All eyes are therefore on the stocks of smallpox vaccines built up by many States to deal with a possible resurgence of smallpox or a bioterrorist attack scenario. In France, the number of doses available is classified data. The last count made public ten years ago evokes more than 82 million doses of “Pourquier vaccine” and of “Sanofi Pasteur vaccine”.
These vaccines, known as first and second generations, are very effective and participated in the eradication of smallpox until 1984. But they present serious adverse effects, such as encephalitis, encephalopathies, eczema vaccinatum, heart damage, etc. As the injected virus replicates in the body, they are also contraindicated in many cases, especially in pregnant women and immunocompromised people.
“These vaccines were well tolerated in the first year of life, but less well when the first injection was given in adulthood,” points out Brigitte Autran, Emeritus Professor of Immunology at the Sorbonne-University Faculty of Medicine. Their use was therefore naturally discarded after the eradication of smallpox. “The risk from the vaccine itself is higher than that of monkeypox, which in almost all cases in healthy people is a very mild infection with a nasty rash,” adds David Freedman.
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