Brief overview
- Description: The smallpox vaccine Imvanex contains non-reproducing live viruses. Because of the close relationship, it protects against both “human” and monkeypox.
- Who should be vaccinated? Homosexual men with frequently changing sexual partners, medical personnel and laboratory staff with an increased risk of infection, people after close contact with infected persons or infectious material.
- Vaccination schedule: Usually two doses at least 28 days apart. For older people who were vaccinated decades ago, one dose is sufficient if they have an intact immune defense.
- Side effects: Headaches, nausea, muscle pain, fatigue and reactions at the injection site (pain, swelling, redness) are very common.
- Contraindications: Hypersensitivity to any component of the vaccine. For safety reasons, do not administer during pregnancy and breastfeeding (except possibly after a positive risk-benefit assessment).
What is the monkeypox vaccine?
Today, doctors vaccinate against monkeypox (Mpox) with a smallpox vaccine that is licensed in the EU as Imvanex and in the USA as Jynneos, which is also licensed against Mpox.
They are therefore considered to be better tolerated overall than the smallpox vaccine used until the 1980s, which was made from live viruses that were still able to replicate.
According to the manufacturer, the protective effect of the vaccine against infection with monkeypox is said to be at least 85 percent. However, it is not yet possible to make any conclusive statements about the exact effectiveness in everyday life, as it has so far mainly been tested in the laboratory.
The older Variola vaccines are also effective against monkeypox. Most of today’s over-50s were still routinely vaccinated before smallpox was eradicated. All of them therefore presumably still have some residual protection against smallpox – and also against monkeypox due to the close similarity of the viruses. However, it is unclear how high this vaccination protection actually is after decades.
After smallpox was successfully eradicated worldwide through vaccination programs, the series vaccinations were suspended. In Germany, smallpox vaccination was compulsory until 1976 – it was finally suspended in 1983.
Who should be vaccinated now?
Imvanex can be administered both preventively (pre-exposure prophylaxis) and after contact with an infected person or with infectious material (post-exposure prophylaxis). Accordingly, the STIKO currently recommends monkeypox vaccination for:
- Men with frequently changing male sexual partners
- Laboratory staff who routinely work with infectious sample material or who have had unprotected contact with non-inactivated monkeypox material
- People who have or have had close physical contact with infected persons via non-intact skin or mucous membranes (e.g. sexual intercourse, kissing, hugging)
- People in medical care who have had close contact without adequate personal protective equipment (FFP2 mask, gloves, etc.) with Mpox sufferers, their body fluids or with potentially infectious material (such as clothing or bed linen)
The risk of infection with monkeypox is high in close – especially intimate – contact. This applies if one of the people involved carries the virus. This transmission route and the risk of infection is the same for all people – regardless of age or gender, whether male, female or diverse.
What’s more, monkeypox is not primarily a sexually transmitted disease anyway! You can become infected through any close physical contact or contact with infectious material: a father with his child, a doctor with her patient, toddlers with each other.
How is the vaccine given?
Imvanex is approved for adults aged 18 and over and is injected under the skin (subcutaneous injection).
In exceptional cases, the monkeypox vaccine can also be administered to children after contact with an Mpox patient or infectious material (post-exposure prophylaxis). This is done outside the approval of the vaccine (“off-label”).
Preventive vaccination
In general, doctors administer two vaccine doses of 0.5 ml each at least 28 days apart.
However, according to experts, anyone who has been vaccinated against smallpox in the past only needs one vaccine dose for a booster – unless they are people with an immune deficiency. These people always receive two doses of vaccine – regardless of any previous smallpox vaccination.
You can read more about vaccinating people with a weakened immune system in the article Immunosuppression and vaccination.
Vaccination after contact
In principle, post-exposure vaccination against monkeypox is advisable up to 14 days after contact with infected persons or infectious material. This means that the first dose of vaccine should be given during this period, and the earlier the better:
Experts believe that vaccination within the first four days of contact is likely to prevent infection. If the first vaccine injection is administered more than four (up to 14 days) after contact, it is unlikely that the disease can be prevented, but it can at least be attenuated.
The post-exposure vaccination is only given if there are no (possible) symptoms of monkeypox (such as fever, headache and muscle pain, swollen lymph nodes, skin changes)! Otherwise, experts advise against giving Imvanex.
Duration of effect of the vaccination
It is currently unclear how long the protection provided by Imvanex lasts. There is therefore no precise information on a booster vaccination. The reason for this is that Imvanex could never be tested “in the wild” due to the lack of occurrence of the disease. The information on efficacy is also based on laboratory tests and not on a tested protective effect in real situations.
What side effects are possible?
Very common side effects (i.e. those affecting more than 1 in 10 people treated) are
- headache
- Nausea
- Muscle pain (myalgia)
- fatigue
- Reactions at the injection site (pain, redness, swelling, hardening and itching)
Less common side effects include chills, fever, joint pain, sore throat, cough, insomnia, vomiting and diarrhea.
People with atopic dermatitis (neurodermatitis) show increased local and general symptoms in response to the vaccination.
Who should not be vaccinated?
Patients who have had an allergic reaction to a previous dose of vaccine or to certain ingredients of the vaccine must not be vaccinated. These may be residual chicken egg white, for example. Such traces are due to certain production steps in the cultivation of the vaccine viruses in hen’s eggs.
As a precaution, Imvanex should not be administered during pregnancy and breastfeeding – unless doctors consider the potential benefits of the vaccination to outweigh the potential risks for mother and child in individual cases.
Possible interactions
To be on the safe side, the monkeypox vaccination should not be administered together with other medications (including other vaccines). Researchers have not yet conducted any studies on possible interactions between Imvanex and other drugs.
