What you need to know about the Imvanex vaccine, recommended for high-risk contacts

The Supreme Health Authority recommended, on Tuesday, the use of third-generation vaccines against smallpox in the context of the spread of monkeypox, a disease close to smallpox.

As monkeypox gradually spreads in Europe and North America, smallpox vaccines are gaining renewed interest in countries where the disease has been detected. These vaccines were abandoned in the 1980s with the eradication of smallpox, and proved 85% effective against monkeypox, due to the proximity of the infections.

Imvanex, a Danish vaccine developed by Bavarian Nordic, is the one getting all the attention. The third generation is known to cause fewer side effects than the smallpox vaccines used in the 1970s. Spain has already announced that it has placed an order for several doses, and the High Authority for Health (HAS) announced on Tuesday that it recommended vaccinating only high-risk contacts of monkeypox patients with this product.

BFMTV.com takes a look at this vaccine, developed in the early 2000s, which is now expected to play a major role in the global response to monkeypox.

• Developed first to respond to a bioterrorist threat

In 1980, the World Health Organization (WHO) officially declared smallpox to be eradicated worldwide. Countries around the world are called upon to destroy virus strains preserved in the laboratory to avoid a bacterial accident. But as a 2006 Ministry of Health document notes, “It is possible (…) that viruses have been illegally stored or obtained.”

Fear that prompted some countries and laboratories to continue working on new formulations of smallpox vaccines. In the United States, the fallout of September 11 justified the development of the BioShield program, aimed specifically at dealing with the smallpox epidemic.

The Danish company Bavarian Nordic, on behalf of the United States, developed the Imvanex smallpox vaccine in the early 2000s, before placing the first order in 2009.

“Since 2010, Northern Bavaria has delivered its vaccine to the US National Strategic Stockpile for emergency use for immunocompromised individuals, such as those with HIV, for whom conventional smallpox vaccines are not recommended. Imvanex has also been made available to other governments in all across the country and the world,” reads a 2013 press release from the Scandinavian state of Bavaria.

• What are the side effects?

If the Imvanex vaccine is now recommended by the Supreme Authority for Health, it is because it presents a lower risk than the “traditional” smallpox vaccines, which were given around the world before the 1980s. Thus, HAS evokes the third generation Imvanex vaccine, “a tolerability profile, better than first and second generation vaccines,” as well as better efficacy.

As HAS specifies in its view, first- and second-generation vaccines require a specific injection technique, with a forked needle, and can present an immune response and serious adverse effects, such as encephalitis and heart damage. For these reasons, they are contraindicated in pregnant women, people with immunodeficiency and children under one year of age.

The Imvanex vaccine, which has been authorized by the European Medicines Agency since 2013, does not have these drawbacks. “It has a more convenient method of administration and safety profile than first and second generation vaccines, while providing similar immunity. Smallpox vaccination has been shown to be 85% effective in preventing monkeypox (English term for “monkey pox,” editor’s note)”, HAS details.

Imvanex is injected using a “traditional” needle in the upper arm. The side effects are slight.

“The most common side effects of Imvanex (which may affect 1 in 10 people) are headache, nausea, muscle aches (muscle pain), fatigue, and injection site reactions (pain, redness, swelling, stiffness, and itching), the European Medicines Agency explains.

• How does this vaccine work?

Imvanex’s technology is based on injecting a “modified live form of the vaccine virus called the ‘Ankara vaccine’ related to the smallpox virus,” according to a report from the European Medicines Agency. Ankara vaccine is not dangerous to humans, and it cannot multiply in human cells.

Thus, the serum “teach” our bodies how to defend itself against disease. When a person receives the injection, the immune system recognizes the virus as a foreign body and makes antibodies to fight it. If exposure to this virus or one close to it is repeated, the antibodies formed during the injection will appear to neutralize it.

Several studies in people who have never received the smallpox vaccine have shown that the level of antibodies after immunization with Imvanex is at least as high as with the conventional smallpox vaccine.

• How many doses are needed?

In its recommendation regarding monkeypox, HAS specifies that people receiving Imvanex vaccine should receive two doses of 0.5ml.

“The initial vaccination schedule includes two doses of 0.5 mL subcutaneously at least 28 days apart between the two doses.”

For people already vaccinated against smallpox, especially people over 50 years of age, the European Medicines Agency recommends a single dose vaccination, except for immunocompromised people, who must receive two doses 28 days apart.

• Who is involved?

Who is the invited audience in France to receive this vaccine? As defined by HAS in its opinion, it is first of all contact cases at risk as well as unprotected health care personnel who have been invited to receive the Danish serum.

It is clear that “any person who has had direct, unprotected physical contact with damaged skin or biological fluids of a probable or confirmed accidental condition, whatever the circumstances, including sexual contact, medical or paramedical care work, sharing toilet utensils, or contact with Textiles (clothing, bathroom linen, and bedding) or soiled dishes used in case of probable or confirmed symptoms.”

But also “anyone who has unprotected contact within 2 meters for 3 hours with a probable or confirmed case of accident”.

For this audience, vaccination should “ideally take place within 4 days after risky contact and at most 14 days after,” adds HAS.

• What is the state of stocks in France?

But does France have enough stocks of Imvanex to vaccinate vulnerable contact cases of monkeypox patients? Yes, the new Health Minister Brigitte Bourguignon responded on Wednesday.

“The stocks are there and we have a strategic stockpile and vaccination will be targeted, and we are not talking about a complete vaccination,” the minister explained during a visit to the Pasteur Institute. Before I add: “The stocks are perfect right now, I can’t tell you more.”

Brigitte Bourguignon said an epidemic outbreak of the disease is also not expected. Seven confirmed cases of the disease were present in France on Wednesday. Monkeypox is first manifested by fever and pain before developing into a rash characterized by impressive blisters.

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