Imvanex live modified vaccinia Ankara virus

What is Imvanex and what is it used for?

Imvanex is a vaccine used to protect against smallpox in adults. It contains a live modified form of the vaccinia virus called ‘vaccinia Ankara’, which is related to the smallpox virus.

Smallpox was officially declared eradicated in 1980 with the last known case of the disease occurring in 1977. This vaccine will be used in situations where it is considered necessary to protect against smallpox in accordance with official recommendations.

How is Imvanex used?

Imvanex is available as a suspension for injection under the skin, preferably in the upper arm. People who have not been previously vaccinated against smallpox should receive two 0.5 ml doses, with the second dose given no less than 28 days after the first.

If a booster dose is considered necessary for those who have been vaccinated against smallpox in the past, a single 0.5 ml dose should be given except for patients with a weakened immune system (the body’s natural defences) who should receive two booster doses, with the second given no less than 28 days after the first.

The vaccine can only be obtained with a prescription.

How does Imvanex work?

Vaccines work by ‘teaching’ the immune system how to defend itself against a disease. When a person is given the vaccine, the immune system recognises the virus in the vaccine as ‘foreign’ and makes antibodies against them. When the person is exposed again to this or a similar virus, these antibodies together with other components of the immune system will be able to kill the viruses and help protect against the disease.

Imvanex contains a modified form of the vaccinia virus called vaccinia Ankara, which does not cause disease in humans and cannot replicate (reproduce) in human cells. Because of its similarities to the smallpox virus, the antibodies produced against this virus are also expected to protect against smallpox. Vaccines containing vaccinia viruses were used effectively in the campaign to eradicate smallpox.

What benefits of Imvanex have been shown in studies?

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 were carried out. The studies involved over 2,000 adults, including patients with HIV and atopic dermatitis (an itchy skin condition caused by an overactive immune system) and people who had been vaccinated against smallpox in the past. Two of the studies specifically looked at the effectiveness of Imvanex as a booster. Although the studies showed that Imvanex is expected to protect against smallpox, it is not possible to determine from study results the exact level of protection or how long the protection would last.

What are the risks associated with Imvanex?

The most common side effects with Imvanex (which may affect more than 1 in 10 people) are headache, nausea, myalgia (muscle pain), tiredness and injection site reactions (pain, redness, swelling, hardening and itching). For the full list of all side effects reported with Imvanex, see the package leaflet.

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 and gentamicin.

Why is Imvanex approved?

The Agency’s Committee for Medicinal Products for Human Use (CHMP) noted that Imvanex is effective at triggering the production of antibodies to a level expected to provide protection against smallpox, although the exact level and duration of protection it would provide in an outbreak is not known.

With regard to safety, the vaccinia virus in Imvanex cannot replicate in human cells and hence is less likely to cause side effects than previous 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.

Taking into account all the data, the CHMP concluded that Imvanex’s benefits are greater than its risks and recommended that it be approved 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 absence of the disease. Every year,  the European Medicines Agency will review any new information that becomes available and this summary will be updated as necessary.

What information is still awaited for Imvanex?

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

What measures are being taken to ensure the safe and effective use of Imvanex?

The company will further study the vaccine in adults not vaccinated before in order to compare the effectiveness of Imvanex with that of a conventional smallpox vaccine.

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

Other information about Imvanex

The European Commission granted a marketing authorisation valid throughout the European Union for Imvanex on 31 July 2013.


European Medicines Agency

This is a summary of the European public assessment report (EPAR) for Imvanex. It explains how the Agency assessed the medicine to recommend its authorisation in the EU and its conditions of use. It is not intended to provide practical advice on how to use Imvanex.

The full EPAR for Imvanex can be found in:

For more information about treatment with Imvanex, read the package leaflet (also part of the EPAR) or contact your doctor or pharmacist.

This summary was last updated in 12-2016.