Evaluation of Long-term Immunogenicity of a Boost Dose of MVA-BN Vaccine

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

RECRUITING

Total Enrollment

90 participants

Study Classification

OBSERVATIONAL

Study Start Date

2025-05-07

Study Completion Date

2027-11-30

Brief Summary

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

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Detailed Description

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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.

Conditions

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Monkeypox

Study Design

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Observational Model Type

COHORT

Study Time Perspective

PROSPECTIVE

Eligibility Criteria

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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

Minimum Eligible Age

18 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

No