Tracking the immune Response After mpoX vaCcination

Brief overview of the Study

The Mbote-TRAXX study is a clinical research project designed to evaluate the immune response following mpox vaccination in Kinshasa, Democratic Republic of the Congo (DRC). The study focuses on individuals vaccinated with either the MVA-BN or LC16m8 mpox vaccines during national vaccination campaigns. Participants will be followed over a 24-month period to assess the development, strength, and durability of both antibody and cellular immune responses after vaccination.

The study also aims to generate locally relevant data in an endemic setting, where factors such as repeated orthopoxvirus exposure, HIV prevalence, co-infections, and nutritional status may influence vaccine-induced immunity. In addition to immunogenicity, the study will document vaccine tolerance and post-vaccination mpox infections.

The intervention of the study consists exclusively of blood sample collection during follow-up visits; vaccination itself is administered independently through the national vaccination program and is not part of the study intervention.

Study Design

Mbote-TRAXX is a prospective clinical study with minimal intervention conducted in Kinshasa, DRC. The study evaluates humoral and cellular immune responses in adults vaccinated against mpox with either MVA-BN or LC16m8 as part of routine national vaccination campaigns.

Approximately 300 participants will be enrolled, including around 150 participants vaccinated with MVA-BN and 150 vaccinated with LC16m8. Recruitment will occur at selected vaccination sites, and eligible participants will be approached after receiving their vaccine.

Participants will attend six follow-up visits over a period of 24 months: baseline (Day 0), Day 28, Day 59, Month 8, Month 16, and Month 24. At each visit, blood samples will be collected to measure binding antibodies (IgG) and neutralizing antibodies against mpox virus (MPXV). In a subgroup of participants, additional blood samples will be collected for cellular immunity analyses, including MPXV-specific T-cell responses.

Clinical and epidemiological information, including medical history, prior vaccination history, mpox exposure risk, vaccine tolerance, and possible post-vaccination mpox infections, will also be documented throughout follow-up.

The study is classified as a minimal-intervention clinical trial because the vaccines are administered outside the study framework through the national vaccination program; the only study-specific intervention is blood sampling.

Objectives

Primary Objective

• Estimate the seroconversion rate of neutralizing antibodies against mpox virus (MPXV) 28 days after administration of MVA-BN or LC16m8 vaccine

Secondary Objectives

• Estimate neutralizing antibody positivity rates at Day 59 and Month 8 after vaccination
• Analyze longitudinal evolution of neutralizing antibody titers over time
• Estimate positivity rates of MPXV binding antibodies (IgG) throughout follow-up
• Analyze longitudinal evolution of MPXV-specific IgG antibody titers
• Identify factors associated with weak immune responses
• Evaluate tolerability of MVA-BN and LC16m8 vaccines
• Document post-vaccination mpox infections

Exploratory Objectives

• Assess MPXV-specific T-cell responses in a participant subgroup
• Compare immune responses between MVA-BN and LC16m8 vaccines
• Compare immune responses between previously exposed and naïve participants

 

NCT07499739

Funder

• Directorate General for Development Cooperation and Humanitarian Aid (DGD)