Longitudinal Bundibugyo Virus Glycoprotein Seroreactivity Following rVSVΔG-ZEBOV-GP Vaccination in Outbreak-Affected Populations of the Democratic Republic of the Congo

ABSTRACT Background There are currently no vaccines approved for the prevention or treatment of Orthoebolavirus bundibugyoense (Bundibugyo virus; BDBV). The recombinant vesicular stomatitis virus–Zaire ebolavirus glycoprotein vaccine (rVSVΔG-ZEBOV-GP; ERVEBO) has been widely deployed during Ebola virus disease (EVD) outbreaks caused by Orthoebolavirus zairense (Ebola virus; EBOV). Given the lack of vaccines and medical countermeasures we evaluated development of antibodies to Bundibugyo glycoprotein (GP) following rVSVΔG-ZEBOV-GP vaccination in two EVD outbreak-affected populations in the Democratic Republic of the Congo (DRC). Methods Between 2018 and 2023, serum samples were collected from vaccine recipients in Mbandaka, Equateur Province (n=482 at baseline), and Beni, North Kivu Province (n=599 at baseline). Antibody reactivity was assessed using a multiplex pan-filovirus immunoassay. We evaluated longitudinal trends in BDBV GP seroreactivity across follow-up visits extending to approximately five years after vaccination. Findings We collected 2552 samples from 482 participants in Mbandaka and 3297 samples from 599 participants in Beni. BDBV GP responses diverged by location. Baseline BDBV GP seroreactivity differed between sites, with 3.3% of participants reactive in Mbandaka and 10.4% in Beni. In Mbandaka, BDBV GP titers remained unchanged through 6 months post-vaccination but increased markedly between 2.5 and 3.5 years (mean MFI 1,238 to 4,845; p