Bikoro, Equateur Province, DRC — 24 July 2018
The Democratic Republic of the Congo (DRC) declared the end of its ninth recorded Ebola outbreak on 24 July 2018, bringing to a close a 77-day emergency response in Equateur Province that resulted in 54 total cases — 38 confirmed and 16 probable — and 33 deaths. The outbreak, declared by the DRC Ministry of Health on 8 May 2018, was the first in which the investigational rVSV-ZEBOV Ebola vaccine was deployed from the very earliest stages of the response.
The World Health Organization (WHO) confirmed that the outbreak was confined to three health zones: Bikoro, Iboko, and Wangata in the city of Mbandaka, the provincial capital situated on the Congo River. The geographic spread to Mbandaka — a city of approximately 1.2 million people with direct transport links to Kinshasa — raised immediate concerns about urban transmission, but rapid case finding, contact tracing, and vaccination contained the virus before it could establish sustained urban spread.
Ring Vaccination: A Milestone in Outbreak Control
The deployment of the rVSV-ZEBOV vaccine (also designated rVSVΔG-ZEBOV), developed by Merck, represented a milestone in the control of Ebola virus outbreaks. The vaccine had previously demonstrated efficacy in a ring vaccination trial conducted in Guinea and Sierra Leone in 2015, where an estimated vaccine efficacy of 100% (95% CI 79.3–100.0, p=0.0033) was observed among immediately vaccinated contacts and contacts of contacts. No cases of Ebola virus disease occurred 10 days or more after vaccination among those who received the vaccine immediately, versus 23 cases among eligible contacts who were not vaccinated or whose vaccination was delayed.
On 21 May 2018, ring vaccination commenced simultaneously in Mbandaka (led by WHO) and Bikoro (led by Médecins Sans Frontières). Merck provided WHO with 8,640 doses of the vaccine, of which 7,540 were available in the DRC — approximately enough for 50 rings of 150 people each. An additional 8,000 doses were made available in the coming days.
The ring vaccination protocol followed clearly defined steps. Social mobilizers first visited communities to explain the process to potentially eligible individuals. Two trained team members then listed all contacts and contacts-of-contacts of a confirmed Ebola case, including absent residents. After eligibility assessment and informed consent, vaccination was administered. Individuals were monitored by a physician for 30 minutes following vaccination, with follow-up home visits on days 3 and 14.
Logistical Challenges in a Remote Setting
The remote location and limited road access to affected populations presented major logistical challenges. Maintaining the required -80°C cold chain for the vaccine in tropical conditions, with limited infrastructure in Bikoro and Iboko, required extraordinary coordination by the Ministry of Health, MSF, WHO, and other partners on the ground.
Photo: Immunology pavilion at the Institut National de Recherche Biomédicale (INRB) in DRC. Credit: WHO Regional Office for Africa
The vaccination teams included Guinean researchers who had conducted the original ring trial in Guinea and Sierra Leone, bringing direct operational experience to the DRC response. The Strategic Advisory Group of Experts on Immunization (SAGE) had recommended in 2017 that for outbreaks of Zaire ebolavirus, the rVSVΔG-ZEBOV vaccine should be used under the Expanded Access framework, with informed consent and in compliance with Good Clinical Practice.
A Multilayered Response
The vaccine was one of several outbreak control measures deployed. The full response included case finding, contact tracing, isolation of suspected cases, prompt laboratory diagnosis, infection control in routine healthcare facilities, safe and dignified burials, community mobilization, and effective response coordination. WHO worked alongside the Ministry of Health, Gavi the Vaccine Alliance, MSF, UNICEF, and other partners including the Ministry of Health of Guinea.
The Bigger Picture
The 2018 Equateur outbreak was the ninth Ebola outbreak recorded in the DRC since the virus was first identified in 1976 near the Ebola River in what was then Zaire. The country has developed significant institutional expertise in responding to Ebola, with the Institut National de Recherche Biomédicale (INRB) serving as the national reference laboratory.
Several study trials involving more than 16,000 volunteers in Europe, Africa, and the Americas had established that the rVSV-ZEBOV vaccine has a good safety profile among persons six years of age and above. The vaccine works by replacing a gene from a harmless virus known as vesicular stomatitis virus (VSV) with a gene encoding an Ebola virus surface protein. It does not contain any live Ebola virus.
The WHO did not declare the Equateur outbreak a Public Health Emergency of International Concern (PHEIC), judging the risk to be manageable with existing resources. This decision would prove correct, as the outbreak was contained within two and a half months.
Sources
- WHO Disease Outbreak News: Ebola virus disease – Democratic Republic of the Congo, 21 May 2018.
- WHO Emergencies: Ebola 2018 — DRC.
- WHO Regional Office for Africa: New Ebola outbreak declared in the Democratic Republic of the Congo.
- European Centre for Disease Prevention and Control: Rapid Risk Assessment — Ebola virus disease outbreak in Equateur Province, DRC, May 2018.
- Human Rights Watch: DR Congo Ebola Outbreak, 6 June 2018.
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