Study Backs Testing Merck Ervebo in DRC Outbreak
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- NEJM study published Wednesday found that Merck's Ervebo vaccine, licensed for the Zaire ebolavirus species, appears to generate antibodies that may offer some cross-protection against the Bundibugyo species currently driving the DRC outbreak, according to first author Edouard Lhomme of the University of Bordeaux
- DRC outbreak has reached nearly 2,500 confirmed cases and close to 1,000 deaths as of Monday, making it the third-largest Ebola outbreak on record and the fastest-growing to date, per WHO figures cited in the article
- WHO's Strategic Advisory Group of Experts on Immunization will consider the cross-protection question at its early October meeting, though the agency has expressed only "lukewarm support" and warned that lab signals may not translate into real-world protection
- Africa CDC is planning a clinical trial testing a two-dose vaccine regimen in health workers, with Doctors Without Borders partnering; IAVI said it intends to supply doses of its investigational Sudan virus vaccine if protocol and DRC authorities give approval
- Lancet commentary noted that of 1,000 confirmed cases with known vaccination status in the current outbreak, only 9 had received Ervebo during the 2018-2020 Zaire outbreak and all 9 survived, while none of the 242 fatal cases had been vaccinated
- University of Toronto modeling study by Isaac Bogach warned that ring vaccination—the standard Ebola control approach—may be less effective here because two-thirds of confirmed deaths never sought care and were only tested post-mortem, severely hampering contact tracing
Why it matters: If cross-protection holds up in clinical trials, health workers in the DRC could have an immediately deployable defense against a Bundibugyo outbreak that has outpaced species-specific vaccines still months from field readiness. A 500,000-dose Ervebo stockpile under UNICEF already exists, but Merck and WHO say doses can only be released at UNICEF's request, putting the October SAGE meeting on the critical path for any real-world test.
