Evaluation of Long-term Immunogenicity of a Boost Dose of MVA-BN Vaccine
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- This is an observational study: the protocol does not assign a study treatment.
- Who it may be relevant to
- Registry conditions: Monkeypox. Basic parameters: from 18 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- France
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
Unsure about the terms? Read our patient guide →
Overview
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.
Primary outcome measures
- Immunogenicity a of a booster dose of MVA-BN vaccine [Time frame: 12 months]
Secondary outcome measures (3)
- Persistence of humoral immunogenicity [Time frame: 24 months]
- Kinetics of the humoral response [Time frame: 24 months]
- Description of cases of Mpox infection [Time frame: 24 months]
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
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Observational model
- Cohort
Study locations
France · 1 center
- CIC 1417Cochin-Pasteur — Paris
Identifiers
NCT: NCT06885853 · APHP250053 · IDRCB:2025-A00095-44