Bavarian Nordic’s mpox vaccine, Jynneos (MVA-BN), is set to be trialled in pregnant and breastfeeding women and infants.

The Phase III trial (PregInPoxVac) will enrol around 350 pregnant women and 250 children aged two years and under to assess the safety and immunogenicity of the MVA-BN vaccine in these populations.

The trial is being conducted in the Boende territory of the Democratic Republic of Congo (DRC), the country at the epicentre of the fast-spreading outbreak declared by the World Health Organization (WHO) as both a continental and global public health emergency. The trial is due to begin early next year.

The randomised controlled trial will evaluate patients over 12 months. In the first stage of the study, two doses of the Jynneos vaccine will be administered to pregnant women before or after birth. Blood samples and breast milk will be collected from a group of mothers and their infants to assess whether maternal antibodies are passed onto the newborn following vaccination via either of these routes. In the trial’s second stage, infants aged six to 24 months old will receive a full or half dose of the vaccine.

Data would be used to expand access to Bavarian Nordic’s vaccine –the only WHO-prequalified mpox vaccine for use in healthy adults and adolescents – to also include pregnant or breastfeeding mothers and infants under two years of age, a population which is at heightened risk of severe complications following mpox infection but are not currently eligible to receive a vaccination.

The study, being funded by the Coalition for Epidemic Preparedness Innovations (CEPI) and Global Health EDCTP3, will be sponsored by the University of Antwerp, Belgium, while the University of Kinshasa in the DRC will be the Scientific Project Leader. Bavarian Nordic will supply the Jynneos doses.

Executive director of Preparedness and Response at CEPI, Dr Nicole Lurie said: “Pregnant women and infants are particularly vulnerable to mpox, but their access to the MVA-BN vaccine will be limited until there is more data about its safety and immunogenicity in these populations.”

CEPI is already supporting two other trials of Bavarian Nordic’s mpox vaccine in Africa. These studies will generate evidence about the vaccine in African populations to help inform vaccination strategies and accelerate additional regulatory approval of Jynneos in endemic countries.

Bavarian Nordic is running a Phase II trial (NCT06549530) to evaluate the immunogenicity and safety of the Jynneos vaccine in children from two years to less than 12 years of age compared to adults aged 18-50 years of age for the prevention of smallpox, mpox and related orthopoxvirus infections.