131. The Sierra Leone Trial to Introduce a Vaccine against Ebola (STRIVE): Evolution of a Clinical Trial During an Ebola Outbreak
Session: Oral Abstract Session: Newer and Older Vaccines in Older Adults
Thursday, October 27, 2016: 11:45 AM
Room: 388-390
Background: In response to the 2014-16 Ebola epidemic in West Africa, CDC in collaboration with the College of Medicine and Allied Health Sciences, University of Sierra Leone (SL) and Ministry of Health and Sanitation initiated a phase 2/3 trial of the rVSV∆G-ZEBOV vaccine (Merck) in 5 districts in SL. A flexible study design was used to respond to the changing epidemiology of the outbreak.

Methods: Eligible healthcare and frontline Ebola response workers were enrolled over a 4-month period and individually randomized to immediate (≤7 days) or delayed (18-24 weeks) vaccination with a single 2 x 107 pfu/mL dose of vaccine. Participants were followed for 6 months after enrollment or vaccination for serious adverse events (SAEs) and Ebola virus disease (EVD).

Results: Enrollment and immediate vaccination occurred from April-August 2015; delayed vaccination ended in December 2015. Approximately 8650 participants enrolled and ~8000 vaccinated. As of 1 May 2016, preliminary data from ongoing safety follow up indicates no vaccine-related deaths or other SAEs; 48 participants were evaluated for EVD and had negative test results. An immunogenicity sub-study (~500 participants) to assess baseline seroprevalence and response to vaccination is ongoing. A stepped wedge design (sequential group vaccination after full enrollment) was initially considered but replaced by phased enrollment with individual randomization to allow earlier initiation of vaccination during an ongoing outbreak, increased likelihood of documenting vaccine efficacy (VE) if the outbreak waned, and flexibility to increase the sample size and study area after study initiation. After another trial demonstrated likely VE, some participants in the delayed group were vaccinated before 18-24 weeks because an Ebola cluster was identified in their district. Ring vaccination, a component of the larger Ebola response, was also implemented in SL; overlap with STRIVE study districts required coordination between the trial and response.

Conclusion: The Ebola response in SL successfully interrupted transmission and VE could not be assessed. STRIVE provides important safety and immunogenicity data to support the application for vaccine licensure, and a newly-developed, flexible research infrastructure to conduct future clinical trials.

Susan Goldstein, MD, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, Mohamed Samai, MBBS, MSc, PhD, College of Medicine and Allied Health Sciences, University of Sierra Leone, Freetown, Sierra Leone, Abu-Bakarr Fofanah, MBBS, Ministry of Health and Sanitation, Freetown, Sierra Leone and The STRIVE Study Team


S. Goldstein, None

M. Samai, None

A. B. Fofanah, None

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