Fast facts about IAVI’s contributions to the 2025 Sudan virus disease outbreak in Uganda

IAVI has provided an investigational Sudan virus (SUDV) vaccine candidate for use in an efficacy ring vaccination trial in Uganda led by the World Health Organization (WHO) that started on Feb. 3. The ring vaccination trial is part of a comprehensive public health response to Uganda’s outbreak of Sudan virus disease (SVD).

Read more about how we are contributing to Uganda’s outbreak response:

Fast facts

• An outbreak of SVD was declared in Uganda on Jan. 30 with a confirmed infection in a health worker who died in Kampala.
• On Feb. 3, 2025, WHO initiated an efficacy ring vaccination trial at Makerere University Lung Institute in Kampala. WHO prioritized evaluation of IAVI’s candidate vaccine, which was already prepositioned in Uganda, as part of a global collaborative effort supporting the country’s SVD outbreak response.
• In 2022, Merck, known as MSD outside the United States and Canada, produced and donated to IAVI vials of rVSV∆G-SEBOV-GP candidate vaccine from existing investigational drug substance to supplement IAVI’s ongoing SUDV vaccine development program.
• IAVI now acts as developer and regulatory sponsor and is responsible for all aspects of future development of rVSV∆G-SEBOV-GP.
• In response to Uganda’s 2025 SVD outbreak, IAVI provided to WHO doses of rVSV∆G-SEBOV-GP for use in the ongoing efficacy ring vaccination trial in Uganda. 
• In addition to having vaccine doses already in country, WHO and the partners working on the response also had in place the protocols and relevant approvals from ethics committees and the local government. Together, these factors enabled health authorities to begin the trial within four days of the initial case confirmation.
• As of Feb. 13, 2025, Uganda has reported nine confirmed cases of SVD and has identified nine rings for inclusion in the ring vaccination trial. They have also identified hundreds of contacts and contacts of contacts and are monitoring suspected cases. Investigations are ongoing to determine the origin of the outbreak.
• No U.S. government resources have been used to support the deployment of the vaccine in Uganda.

• SVD is a severe hemorrhagic fever disease, with case fatality rates ranging from 41% to 100% in previous outbreaks. The virus is an NIAID priority pathogen — meaning it poses the highest risk to national security and public health. Developing countermeasures to SUDV and other filoviruses is an urgent matter of both U.S. and global health security.
• No licensed vaccines or therapeutics are available for the disease caused by SUDV, (species Orthoebolavirus sudanense), and existing vaccines for the disease caused by Ebola virus (species Orthoebolavirus zairense) are not cross-protective for SUDV. The two viruses belong to the same family, cause similarly severe hemorrhagic fever diseases, and are endemic to Africa.
• rVSV∆G-SEBOV-GP has previously been shown to be safe, well-tolerated, and immunogenic in an IAVI-sponsored Phase 1 clinical trial in the U.S. The vaccine candidate has also been shown to be safe, immunogenic, and efficacious in multiple preclinical studies conducted previously. A one-dose vaccine that generates a protective immune response quickly is advantageous during outbreaks.
• A study published recently in the New England Journal of Medicine confirms the high-level effectiveness of ring vaccination in containing Ebola outbreaks in the Democratic Republic of the Congo.
• IAVI’s SUDV vaccine development program uses the recombinant vesicular stomatitis virus (rVSV) vaccine vector platform.
• IAVI has been developing rVSV vaccines for more than 20 years and has been developing rVSV-based vaccines for EIDs since 2018.
• All IAVI’s EID vaccine candidates use the same rVSV vector as ERVEBO^®, Merck’s single-dose Ebola Zaire vaccine that has been critical to other Ebola outbreak responses and is licensed in more than a dozen countries.
• IAVI is developing all our EID vaccines and clinical trials together with experts in endemic countries and a range of partners in the U.S. and Europe.