Safety and immunogenicity of novel adenovirus type 26-and modified vaccinia Ankara-vectored Ebola vaccines: A randomized clinical trial
Cohen KW., Shukarev G., Orzabal N., Van Duijnhoven W., Truyers C., Bachmayer N., Splinter D., Samy N., Pau MG., Schuitemaker H., Luhn K., Callendret B., Van Hoof J., Douoguih M., Ewer K., Angus B., Pollard AJ., Snape MD.
Copyright © 2016 American Medical Association. All rights reserved. Importance: Developing effective vaccines against Ebola virus is a global priority. Objective: To evaluate an adenovirus type 26 vector vaccine encoding Ebola glycoprotein (Ad26.ZEBOV) and a modified vaccinia Ankara vector vaccine, encoding glycoproteins from Ebola virus, Sudan virus, Marburg virus, and Tai Forest virus nucleoprotein (MVA-BN-Filo). Design, Setting, and Participants: Single-center, randomized, placebo-controlled, observer-blind, phase 1 trial performed in Oxford, United Kingdom, enrolling healthy 18- to 50-year-olds from December 2014; 8-month follow-up was completed October 2015. Interventions: Participants were randomized into 4 groups, within which they were simultaneously randomized 5:1 to receive study vaccines or placebo. Those receiving active vaccines were primed with Ad26.ZEBOV (5 × 1010 viral particles) or MVA-BN-Filo (1 × 108 median tissue culture infective dose) and boosted with the alternative vaccine 28 or 56 days later. A fifth, open-label group received Ad26.ZEBOV boosted by MVA-BN-Filo 14 days later. Main Outcomes and Measures: The primary outcomes were safety and tolerability. All adverse events were recorded until 21 days after each immunization; serious adverse events were recorded throughout the trial. Secondary outcomes were humoral and cellular immune responses to immunization, as assessed by enzyme-linked immunosorbent assay and enzyme-linked immunospot performed at baseline and from 7 days after each immunization until 8 months after priming immunizations. Results: Among 87 study participants (median age, 38.5 years; 66.7% female), 72 were randomized into 4 groups of 18, and 15 were included in the open-label group. Four participants did not receive a booster dose; 67 of 75 study vaccine recipients were followed up at 8 months. Novaccine-related serious adverse events occurred. No participant became febrile after MVABN-Filo, compared with 3 of 60 participants (5%; 95% CI, 1%-14%) receiving Ad26.ZEBOV in the randomized groups. In the open-label group, 4 of 15 Ad26.ZEBOV recipients (27%; 95%CI, 8%-55%) experienced fever. In the randomized groups, 28 of 29 Ad26.ZEBOV recipients (97%; 95% CI, 82%-99.9%) and 7 of 30 MVA-BN-Filo recipients (23%; 95% CI, 10%-42%) had detectable Ebola glycoprotein-specific IgG28 days after primary immunization. All vaccine recipients had specific IgG detectable 21 days postboost and at 8-month follow-up. Within randomized groups, at 7 days postboost, at least 86% of vaccine recipients showed Ebola-specific T-cell responses. Conclusions and Relevance: In this phase 1 study of healthy volunteers, immunization with Ad26.ZEBOV or MVA-BN-Filo did not result in any vaccine-related serious adverse events. An immune response was observed after primary immunization with Ad26.ZEBOV; boosting by MVA-BN-Filo resulted in sustained elevation of specific immunity. These vaccines are being further assessed in phase 2 and 3 studies.