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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.
There are two distinct viral clades; one found in the Congo basin of central Africa, and the other in west Africa.
As monkeypox is related to the virus causing smallpox, vaccines designed for smallpox will provide a level of protection. Previous data from Africa suggests that previous vaccines against smallpox may be up to 85% effective in preventing monkeypox infection.
Monkeypox is included in the national list of High Consequence Infectious Diseases (HCID) in England and is a notifiable disease.
Human-to-human transmission occurs through close physical contact by two main routes:
It can also be transmitted from mother to child, and from contact with an infected animal or through eating the meat of an infected animal.
Typically, monkeypox has an incubation period of between 5 and 21 days.
The Smallpox vaccine available is a Modified Vaccinia Ankara – Bavarian Nordic (MVA-BN). It is currently distributed under 2 brand names, although it is the same vaccine.
The brand names are
The vaccine can be administered by the deep sub-cutaneous or intramuscular route (see chapter 4). The preferred site is the deltoid region of the upper arm.
In August 2022, following the emergency use approval by the US Food and Drug Administration, JCVI endorsed the use of a fractional dose (0.1ml) of MVA-BN given by intradermal injection during periods of supply constraints. The approach has also been advised by the European Medicines Agency Emergency Task Force. EMA’s Emergency Task Force advises on intradermal use of Imvanex / Jynneos against monkeypox | European Medicines Agency (europa.eu). A fractional dose intradermal injection for MVA-BN may be administered on the deltoid (the same site recommended for BCG - see Green Book chapters 32 and 4) or on the volar aspect (palm side) of the forearm around 2-4 inches below the ante-cubital fossa (the same site as normally used for Mantoux testing).
The virus used in the vaccine is an attenuated strain that cannot replicate in mammalian cells. It should be considered an inactivated vaccine.
While MVA-BN (Imvanex®) efficacy studies were aimed at understanding its protective efficacy against smallpox, many of the licensing studies have used challenge with monkeypox virus.
The Welsh Government has confirmed that areas with localised outbreaks are being prioritised in the distribution of UK-wide supplies of the monkeypox vaccine. As more stock of vaccine is made available health boards will be notified when they can recommence offering pre-exposure vaccination.
First doses should be prioritised during this outbreak, with the offer of a second dose at a later date, for those who continue to be at an increased risk of exposure. The initial priority is to deliver first doses to as many in the highest risks group as possible. Subject to the evolving epidemiology, a second dose may be advised around 2-3 months later to provide longer lasting protection
JCVI proposed that vaccination should be offered as soon as feasible to gay, bisexual and other men who have sex with men (GBMSM) at highest risk due to a large number of contacts.
The committee agreed that GBMSM at highest risk could be identified amongst those who attend sexual health services, using markers of high-risk behaviour similar to those used to assess eligibility for HIV pre-exposure prophylaxis (PrEP), but applied regardless of HIV status. These risk criteria would include a recent history of multiple partners, participating in group sex, attending sex on premises venues or a proxy marker such as recent bacterial sexually transmitted infection (in the past year).
In view of the current epidemiology and vaccine supply available, wider vaccination in low risk GBMSM individuals or the general population is not advised at this time.
Individuals who are identified through contact tracing of confirmed cases will continue to be prioritised and offered post-exposure vaccination where this is indicated.
There is very limited evidence on the effectiveness of post-exposure vaccination using MVA-BN, and therefore vaccine should be prioritised and individuals be risk assessed for those most likely to benefit. This would be based on timeliness of vaccination following exposure and for individuals at higher risk of severe disease following infection.
It is recommended that post-exposure vaccination of high-risk community or occupational contacts is offered ideally within 4 days of exposure, although may be offered up to 14 days in those at ongoing risk, or those who are at higher risk of the complications of monkeypox.
The JCVI has also recommended that during periods of supply constraint, post exposure vaccination offers should be prioritised. Post exposure vaccination for contacts will be prioritised for those at greater risk of severe disease, including children under the age of five, pregnant women and people who are severely immunosuppressed. In addition, people eligible for pre-exposure vaccination, for example high risk Gay and Bisexual men, may be offered post-exposure vaccination.
Like all medicines, the vaccine can cause side effects, but not everybody gets them. The common side effects are:
The most common side effects reported are at the site of injection. Most are mild to moderate in nature and cleared without any treatment within 7 days. Intradermal (ID) injection was associated with a higher rate of itchiness and local reactions such as erythema and induration when compared to subcutaneous injection, although pain at the injection site was less common than after subcutaneous administration.
Other reactions are rare. For more information on common and rare side effects, see:
(These are external pages and are not monitored by Public Health Wales.)
Wales Monkeypox Training Addendum - These slides are an addendum to current training packages and should be used only in conjunction with “Vaccination against monkeypox using the MVA-BN vaccine: training for healthcare practitioners” 7th September 2022, published by the UKHSA.
Clinical resources and information
Smallpox vaccination against Monkeypox checklist v1 Bilingual
What you need to know Intradermal monkeypox vaccination Billingual
Patient Specific Direction (PSD) Template for Monkeypox vaccination available on the Welsh Medicines Information Centre (WMIC) available at: Monkeypox - Welsh Medicines Information Centre (wales.nhs.uk)