The European Centre for Disease Prevention and Control (ECDC) considers the monkeypox virus to be moderately transmissible among humans. According to the Centre, among MSM who contracted the virus, the most common means of transmission is likely through sexual activity due to intimate contact with infectious skin lesions.
Most cases have been in men. A significant proportion of cases, although not all, are in men who have sex with men (MSM), notably in Canada, Spain, and the UK, with many cases diagnosed in sexual health clinics.
Smallpox vaccines containing vaccinia such as Imvanex (Jynneos) can provide around 85% effectiveness against monkeypox. This protection level is calculated from studies using first generation smallpox vaccines tested in late 1980 in Africa. The UKHSA has begun using Imvanex as post-exposure prophylaxis for close contacts of known cases.