MpoxVax AFRIVAC

The challenge

The MVA-BN vaccine has been shown to provide good protection against mpox infection and has been widely used, including in sub-Saharan Africa. However, several aspects of the vaccine are not well characterised, including the strength of immune responses generated in women and in those with impaired immune systems (for example, due to advanced HIV infection), the durability of these responses and the length of protection after vaccination.

In Europe, the MpoxVax trial evaluating MVA-BN vaccination to prevent mpox infection is collecting important immunogenicity data.  However, the study population predominantly comprises Caucasian gay and bisexual men who have sex with men, reflecting the population most affected by the clade IIb mpox outbreak in Europe. As such, the findings may have limited generalisability to Central African settings, where the epidemiology of mpox differs, and women represent a substantially affected population.

The project

The MpoxVax AFRIVAC project uses the European MpoxVax trial as a template, extending recruitment to additional populations in the Democratic Republic of the Congo, Tanzania and Uganda in collaboration with local partners. By using existing trial materials, the project team has been able to rapidly launch the new studies in Africa.

The key aim of the project is to generate data on the immunogenicity (the ability to provoke an immune response) of the MVA-BN vaccine and the durability of immune responses in African populations, with a focus on women and people living with HIV, who are disproportionately affected by the current mpox outbreak. The studies will also explore other factors, such as age or ethnicity, that could be associated with variation in the strength or duration of vaccine-induced immune responses.

Around 300 people have been recruited from three sites and followed for 48 weeks after vaccination. Analyses are focusing on antibody levels immediately after vaccination and in the following months, providing important information on the magnitude and durability of vaccine-induced immune responses.

The project will also evaluate a previously developed and validated immunological assay in African populations. The assay distinguishes immune responses following mpox infection from those induced by vaccination by measuring responses to selected viral antigens, enabling identification of infection- versus vaccine-derived immunity.

Finally, the project is establishing a regional clinical trials unit to support research across the three participating countries.

MpoxVax AFRIVAC is one of nine projects funded through an emergency call for proposals launched in response to the mpox outbreak in the DRC and other sub-Saharan African countries, which was declared a Public Health Emergency of International Concern (PHEIC) by WHO and a Public Health Emergency of Continental Security (PHECS) by Africa CDC in 2024.

Impact

The MpoxVax AFRIVAC project will provide key information on the immune responses generated by the main vaccine being used to prevent mpox infections. It will:

• Generate data on immune responses in sub-Saharan African populations, including women and people living with HIV, which will provide a likely indication of its effectiveness in the general population and in these specific groups.
• Deliver evidence on the durability of protection and whether and when re-vaccination might be required.
• Establish research skills, knowledge and trial infrastructure in a Central African setting to enable future research in emerging infections and host immune response

With vaccination a key strand of mpox control programmes, the MpoxVax AFRIVAC project will deliver vital evidence for policymakers on how best to use the MVA-BN vaccine.