The vaccine used for the preventive vaccination against Mpox is the smallpox vaccine Imvanex®. Because the smallpox virus and the monkeypox virus are very similar, this vaccine is expected to provide protection against infection with the monkeypox virus.
About the Mpox vaccine
Since 2013, Imvanex® has been registered in Europe as a vaccine to protect against smallpox. Imvanex® is now also registered as a vaccine to protect against Mpox; the vaccine received EMA authorisation on 22 July 2022. Imvanex® contains a live attenuated virus that cannot replicate inside the body. It has milder side-effects than the old smallpox vaccinations, and Imvanex® does not leave a scar.
How it works
We know that Imvanex® is safe and that it produces a good immune response. The vaccine can be safely administered to immunocompromised people, but they may have a weaker immune response. In order to build up good immunity, 2 vaccinations are needed with an interval of at least 4 weeks.
It is not known whether vaccination with Imvanex® can prevent all symptoms of Mpox or transmission of the virus. It is possible that some people may still develop a mild form of the disease and transmit the virus despite vaccination. Even after vaccination, the following recommendations therefore apply: have any blisters examined by your GP or the Municipal Public Health Services (GGDs). If you have symptoms, do not have any intimate contact or sexual intercourse, not even with a condom.
If a person tests positive for Mpox, they must continue self-isolating and follow the rules for isolation, and the GGD will start source and contact tracing.
Research
The effectiveness of the Imvanex® smallpox vaccine in preventing Mpox has only been studied in animals. During animal testing, the vaccine protects against serious infection if the animals are exposed to the monkeypox virus after vaccination. However, there have not been any large-scale clinical trials in humans that have looked at how well the vaccine protects against symptomatic infection or severe disease from monkeypox. For that reason, a study on vaccine effectiveness and side-effects will be launched concurrently with the Mpox vaccination programme.
Available vaccines
The smallpox virus has not been found anywhere in the world since 1980, so there is a limited number of smallpox vaccines in stock worldwide. 70,000 vaccines have been made available for preventive vaccination against monkeypox in the Netherlands. Most European countries currently have far fewer vaccines available. It is not yet clear whether new deliveries can be expected anytime soon.