Clinical trial NCT06885853: Evaluation of Long-term Immunogenicity of a Boost Dose of MVA-BN Vaccine
Official title: Evaluation of Long-term Immunogenicity of a Boost Dose of MVA-BN Vaccine
Study type: OBSERVATIONAL
Overall status: RECRUITING
Conditions: Monkeypox
Keywords: Monkeypox
MVA-BN booster vaccine
HIV pre-exposure prophylaxis
Lead sponsor: Assistance Publique - Hôpitaux de Paris
Sponsor class: OTHER
First posted: 2025-03-20
Enrollment: 90
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: COHORT
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: The study population will consist of Men who have Sex with Men (MSM), taking HIV pre-exposure prophylaxis (HIV PrEP), eligible for MVA-BN vaccination.

Brief summary: This study is to evaluate the long-term immunogenicity of a boost dose of MVA-BN vaccine

Detailed description: Mpox is an endemic zoonosis in Africa, caused by the MPXV virus of which there are two clades: I (former Congo Basin) and II (former West Africa). Since 2022, clade II has emerged globally via sexual transmission, primarily among men who have sex with men (MSM), resulting in a declaration of public health emergency (PHEIC) by the WHO.

In 2023, a clade I epidemic emerged in East Africa with a high case fatality rate (3-5%). In August 2024, the WHO again declared a PHEIC after the spread of clade I to African countries with no previously reported cases and outside Africa, raising fears of higher mortality and transmission.

A 3rd generation vaccine, MVA-BN (Imvanex® /Jynneos®), initially developed against smallpox, was approved in 2022 to prevent mpox. In France, the HAS recommends post- and pre-exposure vaccination for populations at risk: MSM, trans people with multiple partners, sex workers and certain professionals. For people born before 1980 (history of smallpox vaccination), a single dose is recommended as primary vaccination, while immunocompromised subjects require 3 doses.

Data show vaccine effectiveness of 20-80% in post-exposure prophylaxis (PEP) and \~80% in pre-exposure but neutralizing antibodies become undetectable after one year. Since the summer of 2024, the HAS has recommended a booster dose 2 years after the primary vaccination, on the basis of immunogenicity studies showing an increase in seroconversion to 98.7% one month after administration, but underlines the need to have other data, in particular on the durability of this response.

A study is proposed in MSM on HIV PrEP (pre-exposure prophylaxis), a priority population for structured medical monitoring, to evaluate the immunogenicity and safety of the MVA-BN booster in this context.

Eligibility criteria: Inclusion Criteria:

* Men aged over 18 years
* Have received two doses of MVA-BN vaccine as an initial schedule
* Eligible for a booster dose of MVA-BN (according to the HAS recommendation)
* Be eligible and wish to initiate PrEP-HIV treatment or be followed for PrEP-HIV treatment
* Covered by social security (excluding AME)

Exclusion Criteria:

* History of mpox (virologically confirmed)
* Be under guardianship or curatorship
* Be subject to a judicial protection measure
* Have a contraindication to vaccination against mpox

Primary outcomes:
measure: Immunogenicity a of a booster dose of MVA-BN vaccine
timeFrame: 12 months
Secondary outcomes:
measure: Persistence of humoral immunogenicity
timeFrame: 24 months
measure: Kinetics of the humoral response
timeFrame: 24 months
measure: Description of cases of Mpox infection
timeFrame: 24 months
Other outcomes:
Locations:
city: Paris
country: France
facility: CIC 1417Cochin-Pasteur
Study officials:
affiliation: Assistance Publique - Hôpitaux de Paris
name: Liem Binh Luong Nguyen, Degree medical doctor
role: PRINCIPAL_INVESTIGATOR
References: