Imvanex

Recommendations and precautions to be followed by healthcare professionals and patients for the safe and effective use of Imvanex have been included in the summary of product characteristics and the package leaflet.

As for all medicines, data on the use of Imvanex are continuously monitored. Side effects reported with Imvanex are carefully evaluated and any necessary action taken to protect patients.

Imvanex received a marketing authorisation valid throughout the EU on 31 July 2013.

Since Imvanex has been authorised under exceptional circumstances, the company that markets Imvanex will provide data on the vaccine’s benefits and risks from an observational study in people who are given the vaccine, if ever there is an outbreak of smallpox in the future.

The company will also collect data from an observational study that will be carried out during the ongoing monkeypox outbreak in Europe to confirm the effectiveness of the vaccine in protecting against monkeypox.

Imvanex is given by injection under the skin, preferably in the upper arm. People who have not been previously vaccinated against smallpox, mpox or vaccinia viruses should receive two doses, with the second dose given at least 28 days after the first.

If a booster dose is considered necessary in people previously vaccinated, a single dose should be given. People with a weakened immune system (the body’s natural defences) who require a booster should receive two doses, with the second dose given at least 28 days after the first.

The vaccine can only be obtained with a prescription. It should be used in accordance with official recommendations issued at national level by public health bodies.

For more information about using Imvanex, see the package leaflet or contact your doctor or pharmacist.

Imvanex works by preparing the body to defend itself against infection with the variola (smallpox), mpox or vaccinia viruses. It contains a weakened form of the vaccinia virus called ‘modified vaccinia virus Ankara’, a virus that is closely related to the smallpox and mpox viruses but does not cause disease in humans and cannot reproduce in human cells.

When a person is given Imvanex, the immune system recognises the virus in the vaccine as ‘foreign’ and makes antibodies against it. If, later on, the person comes into contact with similar viruses, their immune system will be able to kill the viruses and help protect against disease. Because of the similarity between the virus in Imvanex and the smallpox and mpox viruses, antibodies produced against it are expected to protect against the diseases caused by these viruses.

Imvanex was shown in studies to be effective at triggering the production of antibodies to a level expected to provide protection against smallpox.

Five main studies involved over 2,000 adults, including people with HIV and atopic dermatitis (an itchy skin condition caused by an overactive immune system) and adults who had been vaccinated against smallpox in the past. Two of the studies specifically looked at the effectiveness of Imvanex as a booster. A subsequent study in 433 people who had not been vaccinated before found that the level of protective antibodies after vaccination with Imvanex was at least as high as with a conventional smallpox vaccine. It is not yet known how long the protection will last.

Interim results from an ongoing study involving 211 adults and 315 adolescents aged 12 to 17 years found that the immune response to two doses of Imvanex in adolescents, as measured by the levels of antibodies against the vaccinia virus, was comparable to that seen in adults.

Data from several animal studies showed protection against mpox in non-human primates vaccinated with Imvanex and then exposed to the mpox virus.

Imvanex is also expected to protect against the disease caused by vaccinia virus, since the vaccine is based on a modified version of vaccinia virus.

For the full list of side effects and restrictions with Imvanex, see the package leaflet.

The most common side effects with Imvanex are usually mild or moderate and get better within seven days after vaccination. In adults, the most common side effects (which may affect more than 1 in 10 people) include headache, nausea, myalgia (muscle pain), tiredness and injection site reactions (pain, redness, swelling, hardening and itching). The side effects in children from 12 years old are similar to those seen in adults.

Imvanex must not be used in patients who are hypersensitive (allergic) to the active substance or any of the substances found at trace levels, such as chicken protein, benzonase, gentamicin and ciprofloxacin.

The European Medicines Agency considered that Imvanex is effective at triggering the production of antibodies against smallpox to a level that provides protection at least as high as that from conventional smallpox vaccines. The vaccinia virus in Imvanex cannot replicate in human cells and hence is less likely to cause side effects than conventional smallpox vaccines. Imvanex would therefore be beneficial for people who cannot be given vaccines containing replicating viruses, such as patients with a weakened immune system.

For the prevention of mpox, the Agency considered that the effectiveness of Imvanex could be inferred from animal studies. In addition, because of the similarity between the virus in Imvanex (‘modified vaccinia virus Ankara’) and smallpox, mpox and vaccinia viruses, antibodies produced against it are expected to protect against mpox, smallpox as well as disease caused by the vaccinia virus.

The safety profile of Imvanex is considered favourable, with vaccinated people experiencing mild to moderate side effects. The Agency therefore decided that Imvanex’s benefits are greater than its risks and it can be authorised for use in the EU.

Imvanex has been authorised under ‘exceptional circumstances’. This is because it has not been possible to obtain complete information about Imvanex due to the rarity of the diseases. The company must provide further data on Imvanex. It must submit data on the vaccine’s benefits and risks from an observational study in people who are given the vaccine, if an outbreak of smallpox occurs in the future. In addition, the company will collect data from an observational study carried out during the 2022 mpox outbreak in Europe to confirm the effectiveness of the vaccine in protecting against mpox. The company will also submit the final results of the ongoing study involving 12- to 17-year-old adolescents to provide further information on the safety of the vaccine in this age group.

Every year, the Agency will review any new information that becomes available.