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

Recruiting

• Conditions: Monkeypox

• Registration Number: NCT06885853
• Lead Sponsor: Assistance Publique - Hôpitaux de Paris

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.

Study Timeline

• Study First Submitted: 2025-03-13
• Study First Submitted QC: 2025-03-13
• Study First Posted: 2025-03-20
• Status Verified: 2025-05
• Study Start: 2025-05-07
• Last Update Submitted: 2025-05-14
• Last Update Posted: 2025-05-15
• Primary Completion: 2026-11
• Study Completion: 2027-11

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 90

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

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Primary Outcome Measures

Name	Time	Method
Immunogenicity a of a booster dose of MVA-BN vaccine	12 months	To evaluate the immunogenicity at 12 months of a booster dose of MVA-BN vaccine administered subcutaneously in HIV PrEP users.

Secondary Outcome Measures

Name	Time	Method
Persistence of humoral immunogenicity	24 months	Evaluate the persistence of humoral immunogenicity at 24 months of a booster dose, depending on the number of doses and the interval between doses
Kinetics of the humoral response	24 months	Study the kinetics of the humoral response as a function of the number of doses and the interval between doses
Description of cases of Mpox infection	24 months	Describe cases of Mpox infection based on number of doses and dose interval up to 24 month

Trial Locations

Locations (1)

CIC 1417Cochin-Pasteur; 🇫🇷 Paris, France