To combat monkeypox the authorities chose a traditional method to fight against the virus : educate the immune system by confronting the body with a virus similar to that to be fought. It is therefore a vaccine against human smallpox which is currently used against monkey pox, but of the third generation. Because these two viruses are part of the orthopoxvirus family and human smallpox was eradicated in 1980. The serum currently prescribed uses a third virus of this family, genetically close, that of the initial vaccinia. “There is 90-95% homology of viral proteins implicated between the smallpox and monkeypox viruses”, specifies Olivier Schwartz, head of the virus and immunity unit at the Institut Pasteur. “So taking a very similar vaccine to block it is a strategy which has evidence”.
The current vaccine is not made from animals but from cellular cultureit is said to be “third generation because it has been improved compared to the previous two to limit side effects“, underlines Yannick Simonin, lecturer at the University of Montpellier, specialist in emerging viruses.
High anticipated efficiency
The protection rate of this new vaccine is not yet known, because there is a lack of large-scale data. But epidemiological and laboratory tests anticipate strong efficacy. The latest data available gives a protection figure of 85% in the 90s in Zaire. Having been vaccinated against smallpox before 1980 provides a priori immune protection against monkeypox, of an uncertain extent and duration.
The only vaccine currently authorized by the European Commission for monkeypox is manufactured by the Danish Bavarian Nordic, from the viral strain MVA-BN (modified vaccinia Ankara virus). According to the WHO, there are currently 16 million doses of MVA-BN in the world, mostly in bulk, an agreement provides for the delivery of 7 million additional doses. L’UE has so far ordered 100,000 doses.
Since the beginning of May 2022, more than 18,000 cases have been confirmed worldwide at the end of July 2022, mainly in the United States, Spain, Germany and France (2,400 cases at the beginning of August 2022).