Follow-up of People at Risk of Monkeypox Infection: a Prospective Cohort Study

Indication for Post-Exposure vaccination (PEP) :

PEP has demonstrated its interest in different situations, in particular rabies, tetanus or hepatitis B, as recalled in the report "Guide for post-exposure immunization: vaccination and immunoglobulin" of the High Committee for Public Health in 2016.

For Monkeypox, the PEV was used in 2018 and 2019 in UK, when several import cases were discovered. In 2018, 3 cases were diagnosed and 154 contact cases identified (including 147 healthcare professionals). In total, 131 people have accepted the PEV (including 126 healthcare professionals) and 1 single case among healthcare professionals, having been exposed for 6 to 7 days. In 2019, following an imported case, 17/18 contacts (including children) accepted EPV. No secondary cases or serious adverse effects have been reported.

Several countries have recommended EPV as part of Monkeypox.

Indication for Pre-Exposure vaccination (PrEP):

Since 2022/07/07, in addition to PEP vaccination, HAS recommends vaccination (PrEP) to people at very high risk of infection:

• Men who have sex with men (MSM) reporting multiple partners and trans people reporting multiple sexual partners
• People in prostitution
• Professionals in places of sexual consumption, regardless of the status of these places.

In France, the Haute Autorité de Santé (HAS) recommends that pre-exposure vaccination with 3rd generation MVA-BN vaccines (Imvanex and Jynneos) be offered to female partners who are occasional or who share the same living environment as people at very high risk of exposure, including MSM reporting multiple sexual partners and trans people reporting multiple sexual partners, people in a situation of prostitution and professionals in places of sexual consumption, regardless of the status of these places.

HAS also recommends the implementation of a reactive vaccine strategy with the 3rd generation vaccine administered in 2 doses spaced 28 days apart. For people who received smallpox vaccination with a 1st generation vaccine before 1980, only one dose of MVA vaccine should be administered. For immunocompromised subjects, regardless of their vaccination status, a three-dose schedule, each 28 days apart, is recommended. In post-exposure (PEP) the first dose being ideally administered within 4 days after the risky contact and at most 14 days after the risky contact.

Currently, data on the efficacy of the MVA vaccine used in post-exposure prophylaxis are few. The Centers for Disease Control and Prevention considers it unlikely that 2 doses of MVA vaccine used in PEV will completely prevent infection but believes that rapid vaccination of at-risk contacts could reduce the severity of symptoms.

In France, the definitions for identifying contact persons are :

1. Contact at risk:

• Anyone who has had unprotected direct physical contact, i.e. without wearing surgical masks and FFP2, without using hygiaphones and vis-à-vis direct physical contact, without wearing waterproof gloves (latex, nitrile, rubber) with damaged skin or biological fluids of a probable or confirmed symptomatic case, whatever the circumstances, including acts of medical or paramedical care, or sharing of toilet utensils, or contact with textiles (clothing , bath linen, bedding) or dirty dishes used by the probable or confirmed symptomatic case.
• Anyone who has had unprotected contact at less than 2 meters for 3 hours with a probable or confirmed symptomatic case (e.g. close or intimate friend, transport neighbour, office neighbour, people sharing the same living space with no intimate ties, act of care or hygiene, school and university environment, sports club, etc.). "

1. Confirmed case:

• A positive qPCR or RT-PCR result specific for the MKPXV virus
• A positive result in generic qPCR of the genus Orthopoxvirus, in a person presenting recent risks of exposure to the MKPXV virus in the 3 weeks preceding the onset of the signs (returning from a trip to an endemic zone or where the virus is circulating or at-risk contact of a person returning from a trip to an endemic zone or where the virus is circulating, contact person at risk of a probable or confirmed case).

In order to specify the clinical interest and the safety of MVA vaccination administered in PEP or PrEP in people at risk of infection, it is proposed to set up a national cohort including contact cases falling within the indications for vaccination, i.e. seen within 14 days after the last contact but also people vaccinated with PrEP representing the majority of vaccinations currently.