UK Health Security Agency

Published: 27 May 2022
Publishing reference: GOV-12385


Monkeypox is a rare disease that is caused by infection with monkeypox virus, a DNA virus. With the eradication of smallpox in 1980 and subsequent cessation of smallpox vaccination, it has emerged as the most important orthopoxvirus. Monkeypox occurs sporadically in central and western parts of Africa’s tropical rainforest.

As monkeypox is related to the virus causing smallpox, vaccines designed for smallpox will likely provide a degree of cross-protection. Previous data from Africa suggests that previous vaccines against smallpox may be up to 85% effective in preventing monkeypox infection. In recognition of this protection, there is extant policy in the Green Book (Immunisation Against Infectious Diseases) (1) which recommends that:

“workers in laboratories where pox viruses (such as monkeypox or genetically modified vaccinia) are handled, and others whose work involves an identifiable risk of exposure to pox virus, should be advised of the possible risk and smallpox vaccination should be considered. Detailed guidance for laboratory staff has been prepared (Advisory Committee on Dangerous Pathogens and the Advisory Committee on Genetic Modification, 1990)”.

Historically, first and second generation smallpox vaccines have been used for population-level and targeted occupational health-related immunisation programmes in the UK. These vaccines are reactogenic and associated with risks of other serious adverse events. The newer third generation smallpox vaccines have a much-improved side effect profile compared with first and second generation smallpox vaccines.

The modified vaccinia Ankara (MVA-BN) (Imvanex) vaccine, a third generation smallpox vaccine has been licensed by European Medicines Agency (2) in 2013 for the prevention of smallpox. In September 2019, the Food and Drug Administration (FDA) in the US approved MVA-BN (JYNNEOS) for the prevention of monkeypox as well as smallpox. Although not specifically licensed for the prevention of monkeypox in Europe, this vaccine has been used in the UK in response to previous incidents.

This document summarises the available data on MVA-BN (Imvanex) including from previous experience of use of this vaccine in contacts of monkeypox cases in the UK and details the current advice of an expert working group (see Appendix 1 for details) on the use of this vaccine for pre- and post-exposure use in England. ...