DR Congo

Preliminary results on the efficacy of rVSV-ZEBOV-GP Ebola vaccine using the ring vaccination strategy in the control of an Ebola outbreak in the Democratic Republic of the Congo: an example of integration of research into epidemic response

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DRC’s national research institute, the Institut National pour la Recherche Biomedicale (INRB) and WHO have conducted a preliminary analysis of the data being collected from the ring vaccination protocol. The analysis summarized here includes data between May 1, 2018 and March 25, 2019. This preliminary analysis was completed with the aim to better understand whether or not the rVSV-ZEBOV-GP candidate vaccine is effective and is contributing to prevent cases when delivered using the ring vaccination strategy. A more detailed analysis is being prepared and will be available in a peer-reviewed journal.

The Ebola virus disease (EVD) outbreak in North Kivu and Ituri provinces has recently shown an increase in the number of cases reported by week, after many weeks of overall decline. As of 10 April 2019, 1206 confirmed and probable cases of Ebola virus disease have been reported during this outbreak in the Democratic Republic of the Congo (DRC). There is no licensed vaccine against Ebola Virus Disease.

Ring vaccination using the Expanded Access/Compassionate Use protocol has been recommended by SAGE. It was initiated seven days after the declaration of the outbreak, on 1 August 2018, following approval by the National Regulatory Authority of DRC and the Ethics Review Committee of the Ecole de Santé Pùblique in Kinshasa.

The ring vaccination cohort protocol in the DRC is based on previous experiences in West Africa (2, 3, 4, 5). It is a remarkable example of South to South collaboration, where 45 trained Guinean and Niger researchers have coordinated the field implementation under the leadership of a senior Congolese researcher. Leveraging their experience in clinical trials in West Africa, the Guinean teams have also contributed to train nearly 300 Congolese colleagues. Combining this level of collaboration with the ring vaccination strategy and the rVSV-ZEBOV-GP vaccine should contribute to bringing the current Ebola outbreak in the DRC to an end, and to controlling future outbreaks as effectively and rapidly as possible. Figure 2 summarizes the actions implemented in the field by the ring vaccination teams.

From August 1, 2018 to March 25, 2019, 951 confirmed and probable cases of Ebola virus disease were reported during the analysis period. The ring vaccination research teams were able to define 679 rings and enumerate contacts and contacts of contacts around 776 cases. In addition, 28,888 health care workers/ front line workers (HCWs/FLWs) were vaccinated. Due to security reasons and lack of consent from communities, it was not possible to define rings around 175 (18%) of the cases of Ebola virus disease occurring during this period (figure 1). In all 100,754 contacts and contacts of contacts were listed and 91,492 eligible individuals who provided informed consent were vaccinated (90.8% of all enumerated contacts and contacts of contacts were vaccinated in the defined rings).