Since the Monkeypox (MPOX) epidemic that hit France in 2022, clade IIb of this virus continues to circulate quietly in our country with 126 cases since the beginning of the year. Added to this is the fact that a new clade of MPOX (clade Ib) has emerged in Africa and is spreading rapidly to the Democratic Republic of Congo and other countries on the continent. Faced with this situation, the World Health Organization (WHO) declared a Public Health Emergency of International Concern (PHEIC) on August 14 and the High Authority for Health (HAS) has just updated its vaccination recommendations.
A booster dose recommended
In its new opinion, the HAS confirms the two complementary strategies used in 2022:
- One preventive, for unvaccinated or incompletely vaccinated people at high risk of exposure to the virus.
- The other reactive, for people who have had high-risk contact with identified cases and for immunocompromised people who have had close contact with a high-risk contact person. This reactive vaccination should ideally be administered within 4 days of the first high-risk contact to have optimal efficacy, and at the latest within 14 days.
For people who received their first vaccination in 2022, the HAS recommends that they be given a booster dose because there are still uncertainties about the duration of protection induced by the vaccine. This single booster dose should be administered at a distance from the first vaccination and ideally two years or more after the last dose. However, given the natural immunity conferred by the infection, the HAS does not recommend vaccinating people who contracted MPOX in 2022 or in subsequent years.
The objective of this vaccination is threefold:
- prevent the emergence of clade Ib in France;
- reduce or even eliminate the circulation of clade II in our country;
- build long-term immunity to prepare for possible outbreaks.
Who is affected?
The mode of transmission by intimate and/or sexual contact is mainly observed regardless of the clade. People identified as being at high risk of exposure to the virus and therefore eligible for vaccination are:
- men who have sex with men (MSM) and trans people reporting multiple sexual partners;
- sex workers;
- professionals of sexual encounter places, whatever the status of these places;
- partners or people sharing the same living space as the people mentioned above.
Which vaccine?
The recommended vaccine is the same as that used in 2022, namely the third-generation smallpox vaccine MVA-BN, marketed under the name Imvanex in Europe and Jynneos in the United States. The primary vaccination course consists of two doses spaced at least 28 days apart, or a single dose for people who received a first-generation smallpox vaccine before 1980.
For immunocompromised individuals, the schedule is three doses spaced at least 28 days apart, regardless of history of smallpox vaccination.
Pre-exposure vaccine efficacy was estimated at 82% more than 14 days after two doses.
As this vaccine does not have marketing authorization (MA) for children under 18, post-exposure vaccination must be considered on a case-by-case basis for this population, as part of a shared medical decision.
The HAS proposes a tableau summarizing the different vaccination schedules based on infection and vaccination history.
