Ebola vaccine shows promise in STRIVE trial

NEW ORLEANS — An investigational Ebola vaccine administered to health care professionals and response workers in Sierra Leone was not associated with serious adverse events, according to preliminary phase 2/3 results from the STRIVE trial.

Susan Goldstein, MD, of CDC’s National Center for Immunization and Respiratory Diseases, and colleagues enrolled 8,638 adult participants in five districts in Sierra Leone from April to August 2015. The participants were randomly assigned to receive the rVSV-ZEBOV vaccine (Merck) within 7 days of enrollment or within 18 to 24 weeks of enrollment. Initially, the researchers considered a stepped wedge trial design, but opted to conduct phased enrollment and vaccination to increase the chances of determining vaccine efficacy if the outbreak waned and to be able to vaccinate participants earlier during the ongoing outbreak.

The participants were followed for Ebola virus disease (EVD) and serious adverse events for 6 months after vaccination. Goldstein and colleagues planned to determine vaccine efficacy based on EVD incidence in the vaccinated and deferred (unvaccinated) groups.

According to the data, there were no vaccine-related serious adverse events or deaths among vaccinated participants (n = 8,016). The safety profile of the vaccine was similar to that of other published studies, Goldstein said at IDWeek 2016. Seventy-two participants were evaluated for EVD; all PCR results were negative. However, because no EVD cases occurred, vaccine efficacy could not be determined.

In September 2015, an Ebola case was reported within one of the STRIVE study districts. Consequently, the researchers administered the vaccine early to about 100 unvaccinated participants. No other EVD infections were detected in the district; however, the researchers were not able to determine whether early vaccination contributed to prevention of additional cases.

Further analyses examining the immunogenicity of the vaccine in a subset of more than 500 patients are ongoing.

“As our study comes to an end, we recognize that STRIVE was much bigger than a clinical trial,” Goldstein said. “Yes, we rapidly implemented a clinical trial with over 8,000 people and collected important safety and immunogenicity data that will be used for vaccine licensure, but we also built capacity. We trained over 350 Sierra Leonean staff, developed a clinical trials platform, and enhanced research and response capacity that we hope left the country better positioned to continue this work going forward.” – by Stephanie Viguers

Reference:

Goldstein S, et al. Abstract 131. Presented at: IDWeek; Oct. 26-20, 2016; New Orleans.

Disclosures: The researchers report no relevant financial disclosures.