Humoral and cellular immune response induced by rVSVΔG-ZEBOV-GP vaccine among frontline workers during the 2013-2016 West Africa Ebola outbreak in Guinea.

BACKGROUND: As part of a Phase III trial with the Ebola vaccine rVSVΔG-ZEBOV-GP in Guinea, we invited frontline workers (FLWs) to participate in a sub-study to provide additional information on the immunogenicity of the vaccine. METHODS: We conducted an open-label, non-randomized, single-arm immunogenicity evaluation of one dose of rVSVΔG-ZEBOV-GP among healthy FLWs in Guinea. FLWs who refused vaccination were offered to participate as a control group. We followed participants for 84 days with a subset followed-up for 180 days. The primary endpoint was immune response, as measured by ELISA for ZEBOV-glycoprotein-specific antibodies (ELISA-GP) at 28 days. We also conducted neutralization, whole virion ELISA and enzyme-linked immunospot (ELISPOT) assay for cellular response. RESULTS: A total of 1172 participants received one dose of vaccine and were followed-up for 84 days, among them 114 participants were followed-up for 180 days. Additionally, 99 participants were included in the control group and followed up for 180 days. Overall, 86.4% (95% CI 84.1-88.4) of vaccinated participants seroresponded at 28 days post-vaccination (ELISA- GP) with 65% of these seroresponding at 14 days post-vaccination. Among those who seroresponded at 28 days, 90.7% (95% CI 82.0-95.4) were still seropositive at 180 days. The proportion of seropositivity in the unvaccinated group was 0.0% (95% CI 0.0-3.8) at 28 days and 5.4% (95% CI 2.1-13.1) at 180 days post-vaccination. We found weak correlation between ELISA-GP and neutralization at baseline but significant pairwise correlation at 28 days post-vaccination. Among samples analysed for cellular response, only 1 (2.2%) exhibited responses towards the Zaire Ebola glycoprotein (Ebola GP ≥ 10) at baseline, 10 (13.5%) at day 28 post-vaccination and 27 (48.2%) at Day 180. CONCLUSIONS: We found one dose of rVSVΔG-ZEBOV-GP to be highly immunogenic at 28- and 180-days post vaccination among frontline workers in Guinea. We also found a cellular response that increased with time.

Safety of the rVSV ZEBOV vaccine against Ebola Zaire among frontline workers in Guinea.

BACKGROUND: As part of the ring vaccination trial in Guinea, Front Line Workers were invited to participate in a sub-study to provide additional information on the immunogenicity and safety of rVSVΔG/ZEBOV-GP. Here we summarize the information on the safety follow-up. METHODS: An open-label, non-randomized, immunogenicity evaluation of one dose of rVSVΔG/ZEBOV-GP was conducted in Conakry, Guinea between March 2015 and July 2016. Front-line workers refusing vaccination were invited to participate as a control group. Participants were followed for 3 months with a subset followed-up for 6 months after vaccination. Women becoming pregnant during the follow-up were followed until pregnancy outcome. Solicited and unsolicited adverse events were monitored at each contact with participants using standardized study forms. RESULTS: 2016 vaccinated participants and 99 controls were included in the safety cohort. On the 3 days post-vaccination visit adverse events were very common, with over 70% of participants reporting at least one adverse event. The most frequently reported symptoms were headache, fatigue, arthralgia, subjective fever and myalgia. Among participants that completed fever diaries (n = 887), post-vaccination fever was reported by 15.22%. Comparing to the unvaccinated group, local reaction, fatigue, headache, arthralgia, myalgia and subjective fever occurring within the first 3 days post-vaccination were statistically significantly different in the vaccinated group compared to the unvaccinated. A total of 8 Serious Adverse Events were identified during follow-up. 2 SAEs were related to pregnancy. CONCLUSIONS: Results confirm that adverse events 3 days after vaccination with the rVSV candidate vaccine are common. The occurrence of fever is of particular concern in the context of ongoing Ebola transmission. Additional studies should address important data gaps regarding the use of the vaccine in pregnancy and other vulnerable populations.