Adenovirus type-5 vector-based Ebola vaccine was safe and immunogenic in healthy adults

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A recombinant adenovirus type-5 vector-based vaccine expressing the glycoprotein of Ebola Zaire Makona variant showed good safety and immunogenicity in a phase 1 trial of healthy Chinese adults. We aimed to assess the safety and immunogenicity of this vaccine in healthy adults in Sierra Leone and to determine the optimal dose


We did a single-centre, randomised, double-blind, placebo-controlled, phase 2 clinical trial at Sierra Leone–China Friendship Hospital, Freetown, Sierra Leone. We recruited healthy adults aged 18–50 years who were HIV negative, had no history of Ebola virus infection, and had no previous immunisation with other Ebola vaccine candidates. Participants were sequentially enrolled and randomly assigned (2:1:1), by computer-generated block randomisation (block size of eight), to receive the high-dose vaccine (1·6 × 10¹¹ viral particles), low-dose vaccine (8·0 × 10¹⁰ viral particles), or placebo (containing only vaccine excipients, with no viral particles). Participants, investigators, and study staff (except two study pharmacists) were masked from treatment allocation. The primary safety outcome was occurrence of solicited adverse reactions within 7 days of vaccination, analysed by intention to treat. The primary immunogenicity outcome was glycoprotein-specific antibody responses at days 14, 28, and 168 after vaccination, analysed in all vaccinated participants who had blood samples drawn for antibody tests. The trial is registered with the Pan African Clinical Trials Registry, number PACTR201509001259869, and is completed.


During Oct 10–28, 2015, 500 participants were enrolled and randomly assigned t...