rVSV

An rVSV-platform Bundibugyo ebolavirus vaccine candidate is six to nine months from trial readiness as of May 2026, making it the furthest from deployment of the active Ebola vaccine development tracks. No human safety data yet exists for the Bundibugyo-specific rVSV candidate; the existing rVSV-based licensed vaccine, Ervebo, covers only Zaire ebolavirus. In the current DRC and Uganda outbreak, approximately 2,000 doses of Ervebo sit in DRC; WHO experts are examining whether a Zaire-strain vaccine could be used under a trial protocol in a Bundibugyo outbreak, a clinically uncertain proposition.

Recombinant vesicular stomatitis virus (rVSV) is a vaccine delivery platform that replaces a surface glycoprotein of the vesicular stomatitis virus with the glycoprotein of the target pathogen, in this case ebolavirus. The resulting construct is replication-competent, meaning it spreads and amplifies within the recipient, which produces a strong, rapid immune response typically from a single dose. The platform was used in Ervebo (rVSV-ZEBOV), developed by Merck and licensed in 2019, which became the world's first approved Ebola vaccine after demonstrating high efficacy in a ring-vaccination trial during the 2018-2020 DRC outbreak.

rVSV's key advantage is speed of immune response: Ervebo demonstrated protection within ten days in the DRC trial. Its limitation is species specificity: swapping in a Bundibugyo glycoprotein to create a Bundibugyo-specific vaccine candidate requires new manufacturing runs and fresh safety evaluation. The six-to-nine-month timeline to trial readiness reflects that pre-clinical and manufacturing work, not a fundamental platform constraint. If the current outbreak extends, the rVSV Bundibugyo candidate remains a viable medium-term option.