On Tuesday, the High Authority for Health recommended the use of third-generation smallpox vaccines 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 is detected. Abandoned in the 1980s with the eradication of smallpox, these serums prove to be 85% effective against monkeypox, due to the proximity between the two infections.
Imvanex, a Danish vaccine developed by the firm Bavarian Nordic, is the one getting all the attention. Third-generation, it is reputed to cause fewer side effects than the smallpox vaccines used in the 1970s. Spain has already announced that it has placed an order for many doses, and the High Authority for Health (HAS) announced on Tuesday that it recommended the vaccination of at-risk contact cases of monkeypox patients only with this product.
BFMTV.com takes a look back at this vaccine developed in the early 2000s, which is now expected to play a major role in the global response to monkeypox.
• First developed to respond to a bioterrorist threat
In 1980, the World Health Organization (WHO) officially declared smallpox eradicated worldwide. States around the world are invited to destroy their laboratory-preserved strains of the virus, to avoid a bacteriological accident. But as a 2006 document from the Ministry of Health points out, it is « possible (…) that viruses have been stored or obtained illegally ».
A fear which pushes certain countries and laboratories to continue to work on new formulas of smallpox vaccines. In the United States, the repercussions of September 11 justified the development of the BioShield program, intended in particular to deal with a smallpox epidemic.
It was on behalf of the United States that Bavarian Nordic, a Danish company, developed its smallpox vaccine Imvanex in the early 2000s, before a first order was placed in 2009.
« Since 2010, Bavarian Nordic has delivered its vaccine to the U.S. National Strategic Stockpile for emergency use in immunocompromised individuals, such as those with HIV, for whom injection of traditional smallpox vaccines is not recommended. Imvanex has also been provided to other governments around the world, » reads a 2013 press release from Bavarian Nordic.
• What side effects?
If the Imvanex vaccine is now recommended by the High Authority for Health, it is because it presents less risk than the « traditional » smallpox vaccines, which were administered throughout the world before the 1980s. The HAS thus evokes for the Imvanex vaccine, third generation, a « tolerance profile, better than that of the 1st and 2nd generation vaccines », as well as better efficacy.
As the HAS specifies in its opinion, the 1st and 2nd generation vaccines required a particular injection technique, with a bifurcated needle, and could present an immunological response and serious adverse effects, such as encephalitis and cardiac damage. For these reasons, they are contraindicated in pregnant women, immunocompromised people and children under one year old.
The Imvanex vaccine, authorized by the European Medicines Agency since 2013, does not have these disadvantages. « It has a much more favorable mode of administration and safety profile than 1st and 2nd generation vaccines, while providing comparable immunogenicity. Smallpox vaccination has been shown to be 85% effective in preventing of Monkeypox (the English term for ‘monkey pox’, editor’s note) », details the HAS.
Imvanex is injected using a « conventional » needle in the upper arm. As for the side effects, they are minor.
« The most common side effects with Imvanex (which may affect 1 in 10 people) are headache, nausea, myalgia (muscle pain), fatigue and injection site reactions (pain, redness, swelling, hardening and itching) », explains the European Medicines Agency.
• How does this vaccine work?
Imvanex’s technology is based on the injection of a « live modified form of the vaccinia virus called ‘vaccine Ankara’ related to the smallpox virus », details a report from the European Medicines Agency. The Ankara vaccine is not dangerous for humans, and cannot reproduce in human cells.
Thus, the serum will « teach » our body how to defend itself against disease. When a person receives the injection, their immune system identifies the virus as a foreign body and makes antibodies to fight it. If an exposure to this virus or one close to it recurs, the antibodies made during the injection will show up to neutralize it.
Several studies in people who have never received the smallpox vaccine have shown that the level of antibodies after vaccination with Imvanex is at least as high as with a conventional smallpox vaccine.
• How many doses are needed?
In its recommendation concerning monkeypox, the HAS specifies that people receiving the Imvanex vaccine should receive two doses of 0.5ml.
« The primary vaccination schedule includes two doses of 0.5 ml administered subcutaneously with an interval of at least 28 days between the two doses ».
For people who have already been vaccinated against smallpox, mainly people over the age of 50, the European Medicines Agency recommends the inoculation of a single dose, with the exception of immunocompromised people, who should receive two doses 28 days apart.
• Who is concerned?
Which public is called in France to receive this vaccine? As the HAS specified in its opinion, it is first of all at-risk contact cases as well as unprotected healthcare personnel who are invited to receive the Danish serum.
Clearly, « any person who has had direct unprotected physical contact with the damaged skin or biological fluids of a probable or confirmed symptomatic case, whatever the circumstances, including sexual intercourse, acts of medical or paramedical care, or sharing toilet utensils, or contact with textiles (clothing, bath linen, bedding) or dirty dishes used by the probable or confirmed symptomatic case ».
But also “anyone who has had unprotected contact within 2 meters for 3 hours with a probable or confirmed symptomatic case”.
For this public, vaccination must take place « ideally within 4 days after the risky contact and at most 14 days later », adds the HAS.
• What is the state of stocks in France?
But does France have sufficient stocks of Imvanex to vaccinate at-risk contact cases of monkeypox patients? Yes, replied the new Minister of Health Brigitte Bourguignon on Wednesday.
« The stocks are there, we have strategic stocks and it will be targeted vaccination, we are not talking about total vaccination », indicated the minister during a trip to the Pasteur Institute. Before adding: « Stocks are perfect for now, I can’t tell you more ».
No epidemic outbreak of the disease is also expected, said Brigitte Bourguignon. On Wednesday, 7 proven cases of the disease were present in France. Monkeypox is first manifested by fever, pain, before evolving into rashes, characterized by impressive pustules.