Mpox vaccine

While anyone can get mpox, cases in the UK are predominantly in gay and bisexual men, and other men who have sex with men (GBMSM), with the virus being passed on in closely connected sexual networks. As a result, the UKHSA currently recommends the vaccine for those men at higher risk of getting the virus, such as those who have multiple partners, participate in group sex or attend ‘sex on premises’ venues.

The infection is only transmitted easily by close and intimate contact, including skin-to-skin contact so the vaccine is only being offered to those people who are likely to have very close or frequent contact with cases. By offering the vaccine to these individuals, it is hoped that spread of the infection will be curtailed, thus reducing the risk to the whole population. The vaccine is not being offered to GBMSM who have fewer partners who have much lower chance of coming into close contact with a case.

A smallpox (Modified Vaccinia Ankara (MVA)) vaccination is being offered to people who are most at risk to help protect them against mpox. As mpox is caused by a virus similar to smallpox, vaccines against smallpox are expected to prevent or reduce the severity of the monkeypox infection. When you are given the vaccine, your immune system (the body’s natural defence system) produces antibodies against the smallpox virus. These antibodies should also protect you against the mpox virus.

The vaccine contains a virus which has been modified so that it cannot grow or multiply in the human body. This MVA vaccine was developed as a much safer form of the smallpox vaccine used widely in the UK and abroad into the 1970s. The MVA vaccine does not contain smallpox virus and cannot spread or cause smallpox.

In line with UKHSA and JCVI guidance, we are offering a two dose course, with the 2nd dose administered at least 28 days after the 1st dose, to those at highest risk in order to optimize protection against the virus, while continuing efforts to maximize uptake of the 1st dose within this group. This is a fair way to provide some protection to the whole community.

No vaccine is 100% effective but while the vaccine may not always prevent an individual getting mox, the symptoms experienced are likely to be milder. The first dose prepares your immune system so it can respond much more quickly if you come into contact with mpox.  Recent analysis has shown that a single dose of the smallpox vaccine provides around 78% protection against mpox 14 days after vaccination.  After 2 doses of vaccine, almost all people develop antibodies and so should have a good level of protection against mpox. 

While you are waiting for your vaccine, or if you have just received one, please be aware of the risks, and remain alert to the symptoms, of mpox, and be careful when attending events and situations where close contact may occur, especially if you have had a new or multiple sexual partners.

Symptoms can take up to 3 weeks to develop, so keep checking yourself after intimate contact with others. Common signs and symptoms of mpox infection include fever, headache, muscle aches, exhaustion, swollen lymph nodes, and development of a new rash. This could be a single blister like spot (or a small number) on the genitals, anus and surrounding area, lesions in the mouth, and symptoms of proctitis (anal or rectal pain or bleeding).

The only people who cannot receive the vaccine are those who suffered a sudden life-threatening allergic reaction to a previous dose of the vaccine, or any ingredient of vaccine before. This includes those with severe egg allergy as the vaccine contains trace amounts of chicken protein, as well as benzonase and gentamicin and ciprofloxacin (antibiotics).

You should also tell your clinician if you have atopic dermatitis (a form of eczema), as the risk of side effects from the mpox vaccine may be higher. They will discuss with you whether or not going ahead with vaccination is appropriate.

Yes. The vaccine should pose no risk to those who are immunosuppressed, including those with HIV infection who have a low CD4 cell count, as it contains a virus which has been modified so that it cannot grow or multiply in the human body.

Vaccination should generally proceed in accordance with recommendations as individuals with immunosuppression are also at significant risk of the complications of mpox infection. However, the vaccine may not protect you as well which means you could be vulnerable to catching mpox, even if you’ve been vaccinated.

If you are ill with a high temperature you may need to be assessed to determine if you are displaying early signs of mpox. If your illness is not related to mpox, you may still be offered the vaccine. The presence of a minor infection without a fever, such as a cold, should not require postponement of vaccination, but talk to your clinician first.

If you are acutely unwell with more significant symptoms, you may be advised to delay vaccination. This is to both reduce risks of exposing others to your illness and to avoid wrongly attributing any signs or symptoms of your illness to the adverse effects of the vaccine.

It isn’t known if having had mpox infection protects against future infection, but it is considered that re-infection is unlikely, particularly in the short term. Because of this, although previous mpox infection does not mean the vaccine will be harmful, given the constraints on vaccine supply, vaccination of confirmed mpox cases is not currently recommended, even once recovered.

Individuals who have received a smallpox vaccine prior to the 2022 mpox infection outbreak are not currently being prioritised for vaccination as they are considered likely to have a degree of immunity against mpox infection and so be less likely to be infected by the virus.

The smallpox vaccine can safely be given at the same time as other important vaccines including those against HPV and hepatitis. There is no need to observe an interval between the different vaccines.

The vaccine can also be taken safely by those who are taking for pre-exposure prophylaxis (PrEP) for HIV.

The vaccine is given by injection into the muscle of the upper arm (i.e. via the intramuscular route) in a similar way to many other injections.

The vaccine has a very good safety profile. Like all medicines, it can cause side effects, but most of these are mild and short-lived and not everyone gets them. Unlike the old smallpox vaccine, vaccination does not leave a scar.

Common side effects include pain and itching at the injection site and headache, muscle ache, sickness and tiredness. About 1 in 10 people will have chills and fever, but these should not last more than a few days. If you experience any of the side effects listed above, you should rest and you can take the correct dose of paracetamol to help relieve the symptoms.

If you already have atopic dermatitis (a form of eczema), you may experience more intense local skin reactions (such as redness, swelling and itching) and other general symptoms (such as headache, muscle pain, feeling sick or tired), as well as a flare-up or worsening of your skin condition.

Some other conditions have been more rarely reported in people who received the vaccine. In the spirit of openness, the vaccine information leaflet mentions all these conditions – even those reported from single cases – but this does not mean that the vaccine was responsible. If you get any side effects of concern, talk to your clinician.