Haute Autorité de Santé – Monkeypox: the reactive vaccine strategy specified for first-time recipients and children

On May 20, 2022, HAS published an initial recommendation for a vaccine strategy against the virus Monkeypox (monkey pox). It was subsequently contacted by the Director General of Health in order to provide details on the reactive vaccination strategy for two population groups: first-time recipients and children. To do this, in its opinion of June 16, 2022, HAS took into consideration the definition of cases and contact persons at risk according to Public Health France (SPF), the opinion of the National Agency for the Safety of Medicines and health products (ANSM) [Lien de l’avis] concerning the vaccination of persons who had already been vaccinated against smallpox in childhood and the use of the smallpox vaccine of 3e generation in children, the WHO recommendations dated June 14, 2022 as well as several studies and clinical trials.

One dose for first-vaccinated at-risk contact cases, three if they are immunocompromised

Preventive vaccination against human smallpox was compulsory in France until the 1980s (1979 for primary vaccination, 1984 for boosters). To establish, with or without a document justifying vaccination, proof of prior smallpox vaccination, the HAS retains the presence of an indelible waffle scarcharacteristic in people who have been vaccinated with a vaccine of 1re or 2e generation.

While several studies referenced in the HAS opinion have demonstrated the persistence of the immune response in individuals vaccinated against human smallpox in childhood, three clinical trials have also shown that the administration of a dose of Imvanex® in a person who has previously received a primary vaccination with another type of smallpox vaccine confers a booster effect, even very far from this primary vaccination.

The HAS therefore recommends the administration of a single dose of the Imvanex vaccine® for at-risk contact persons who have received smallpox vaccination with a vaccine of 1re generation before 1980.

In the particular case where the contact persons at risk are immunocompromised patients, previous vaccination with another smallpox vaccine does not modify the vaccination schedule initially recommended in this population, i.e. 3 doses of Imvanex®.

Vaccination of post-exposure minors to be considered on a case-by-case basis

The number of cases of virus infection Monkeypox is progressing rapidly in France but does not currently concern children. While smallpox vaccination has long been implemented in infants and young children with first and second generation vaccines prior to smallpox eradication, the Imvanex vaccine® is only allowed in adults.

To issue its opinion, HAS analyzed the available studies. Several of them, carried out in African countries, show that children are more likely to develop serious forms of the disease and that mortality is also higher in this population. During the epidemic that affected the United States in 2003, among the 35 laboratory-confirmed cases (of the 71 declared cases), 11 were children aged 6 to 18, of whom 2 developed a severe form of the disease. sickness.

Furthermore, although the Imvanex vaccine® is currently authorized only in adults, several studies concerning other vaccines using the same platform as Imvanex® (le Modified Virus Ankara – MVA), at higher doses than those recommended for Imvanex®, demonstrated good tolerance in children over 4 months of age. Additionally, no adverse effects were reported following vaccinations – including of children and infants – during the UK outbreak in 2018 and 2019.

HAS also relied on the opinion of the ANSM which points out that the immunogenicity data are insufficient to allow a full decision on the benefit/risk ratio concerning the administration of smallpox vaccines from 3e generation in the pediatric population. However, the ANSM considers that security data history obtained with vaccines from 1re generation (the vaccine was used from the age of 1 year) as well as the safety data available concerning the “MVA platform” used as a vector for immunization against other pathogens (Ebola virus, malaria and tuberculosis) are in favor of the use of vaccines from 3e generation, after a case-by-case assessment for each child, as part of post-exposure reactive vaccination.

Based on these different elements, HAS:

  • Proposes that reactive vaccination of child contacts at risk (as defined by SpF) could be considered to protect children exposed and possibly more likely to develop severe forms of the disease, in particular the most fragile and immunocompromised. However, in the absence of clinical data on the safety of 3rd generation vaccines (indirect, reassuring safety data being nevertheless available), HAS recommends that the vaccination of persons under 18 be considered on a case-by-case basis, by specialists only and after a strict assessment of the benefits and risks for the minor concerned, within the framework of a shared medical decision, and with the consent of the parents (or the legal guardian of the child), and of the teenager if applicable.
  • Recommends the acceleration of the conduct of clinical trials in the pediatric population evaluating the efficacy and safety of third-generation smallpox vaccines with a view to an extension of indication in the pediatric population by the EMA.

HAS will adapt this preliminary recommendation as soon as data from clinical trials in the pediatric population are available. and based on new epidemiological and clinical data. It stresses the importance of soon having more precise data on the mode of human-to-human transmission for the cases currently identified, epidemic monitoring data and additional real-life data relating to the efficacy and tolerance of the smallpox vaccine. of 3e generation, administered pre-exposure and post-exposure to the virus Monkeypoxon the prevention of severe forms and on the transmission of the disease in the various population subgroups, as well as data relating to the efficacy and tolerance of a booster dose in people who have been vaccinated against smallpox in their childhood.

Finally, the cases identified in France concerning men having sex with one or more men (MSM), You have insists on the necessity to inform them of the risks of transmission during physical contact close together or intimate. She also recalls the importance to comply with measures to prevent the transmission of virus Monkeypox both for the general public and for nursing staffas recommended by the High Council for Public Health in his opinion of 24 last may.

Find the full opinion of the HAS