Ebola vaccination strategy — DTM&H MCQ

Correct answer: A — Ring vaccination of contacts and contacts of contacts

The correct answer is A, ring vaccination of contacts and contacts of contacts. This is the strategy validated for rVSV-ZEBOV during Ebola outbreaks: once a confirmed case is identified, vaccination teams trace and offer the vaccine to all direct contacts and their contacts, creating an immunological ring that isolates the virus and interrupts onward transmission. This approach was proven in the Ebola ca Suffit cluster-randomised trial in Guinea, in which investigators tested the effect of rVSV-ZEBOV in preventing Ebola virus disease in contacts and contacts of contacts of recently confirmed cases, and it has since been used operationally in outbreaks in the Democratic Republic of Congo. Ring vaccination is efficient in resource-limited, rapidly evolving outbreak settings because it concentrates a scarce vaccine supply on the highest-risk population rather than requiring mass immunisation logistics across an entire region. Why the other options are wrong: B. Mass vaccination of the entire province: this would require far larger stockpiles and infrastructure than are available during an active outbreak, and is not how limited outbreak vaccine supply is allocated; targeted ring vaccination achieves control with a fraction of the doses. D. Pre-exposure vaccination of all healthcare workers nationally: healthcare workers in outbreak-affected areas may receive pre-exposure doses as an adjunct, but this is not the core outbreak-control strategy and does not address community transmission chains. C. Targeted vaccination of children under 5 only: rVSV-ZEBOV licensing and outbreak use has focused on adults and contacts regardless of age band rather than a paediatric-only strategy, and Ervebo is not routinely given to young children in outbreak protocols. E. Post-exposure vaccination within 24 hours of contact: there is no rigid 24-hour cut-off; contacts are vaccinated as soon as identified during contact tracing, which may be several days after exposure, not bound to a strict single-day window. Key point: rVSV-ZEBOV outbreak control relies on ring vaccination, immunising contacts and contacts of contacts around each confirmed case to rapidly build a protective barrier and halt spread.

Reference: Henao-Restrepo AM et al. Efficacy and effectiveness of an rVSV-vectored vaccine in preventing Ebola virus disease: final results from the Guinea ring vaccination, open-label, cluster-randomised trial (Ebola Ca Suffit!). The Lancet 2017;389:505-518. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(16)32621-6/fulltext