Ring vaccination with rVSV-ZEBOV under expanded access in response to an outbreak of Ebola virus disease in Guinea, 2016: an operational and vaccine safety report

Abstract

Background: In March, 2016, a flare-up of Ebola virus disease was reported in Guinea, and in response ring vaccination with the unlicensed rVSV-ZEBOV vaccine was introduced under expanded access, the first time that an Ebola vaccine has been used in an outbreak setting outside a clinical trial. Here we describe the safety of rVSV-ZEBOV candidate vaccine and operational feasibility of ring vaccination as a reactive strategy in a resource-limited rural setting.

Methods: Approval for expanded access and compassionate use was rapidly sought and obtained from relevant authorities. Vaccination teams and frozen vaccine were flown to the outbreak settings. Rings of contacts and contacts of contacts were defined and eligible individuals, who had given informed consent, were vaccinated and followed up for 21 days under good clinical practice conditions.

Findings: Between March 17 and April 21, 2016, 1510 individuals were vaccinated in four rings in Guinea, including 303 individuals aged between 6 years and 17 years and 307 front-line workers. It took 10 days to vaccinate the first participant following the confirmation of the first case of Ebola virus disease. No secondary cases of Ebola virus disease occurred among the vaccinees. Adverse events following vaccination were reported in 47 (17%) 6-17 year olds (all mild) and 412 (36%) adults (individuals older than 18 years; 98% were mild). Children reported fewer arthralgia events than adults (one [<1%] of 303 children vs 81 [7%] of 1207 adults). No severe vaccine-related adverse events were reported.

Interpretation: The results show that a ring vaccination strategy can be rapidly and safely implemented at scale in response to Ebola virus disease outbreaks in rural settings.

Funding: WHO, Gavi, and the World Food Programme.

Figure 1

Probable chain of transmission in Guinea, from February to April, 2016 (A) Chain of transmission. (B) Date of confirmed cases refers to date of an RT-PCR positive diagnosis. Reproduced from Diallo and colleagues, by permission of Oxford Journals. G=case in Guinea. L=case in Liberia. M=male case. F=female case. NA=not available. *Died. †Possible date of onset.

Figure 2

Map of west Africa and location of Nzérékoré prefecture The flight path indicates how the vaccination teams travelled from Conakry to Nzérékoré. The inset map indicates the location of the four rings defined by their index cases and their contacts and contacts of contacts, including those resident in satellite sites.

Figure 3

Timeline of operations in the four rings in Guinea