(HealthDay News) — For healthy adults from Sierra Leon, the recombinant type-5 vector-based Ebola vaccine is safe and immunogenic, according to a study published online Dec. 21 in The Lancet.

Feng-Cai Zhu, from the Jiangsu Provincial Center for Disease Control and Prevention in Nanjing, China, and colleagues recruited healthy HIV-negative adults aged 18 to 50 years, with no history of Ebola virus infection and no previous immunization with other Ebola candidate vaccines. Five hundred participants were randomized to receive high-dose vaccine (1.6 × 1011 viral particles; 250 participants), low-dose vaccine (8.0 × 1010 viral particles; 125 participants), or placebo (125 participants).

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The researchers found that at least one solicited adverse reaction was reported by 53, 48, and 43 percent of participants in the high-dose, low-dose, and placebo groups, respectively, within seven days of vaccination; most were mild and self-limiting. Vaccine recipients more often had solicited injection-site adverse reactions (26 and 25 percent in the high- and low-dose groups, respectively, versus 17 percent in the placebo group; P = 0.0169). In the low- and high-dose groups, glycoprotein-specific antibody responses were detected from day 14 onward (geometric mean titer, 1,251.0 and 1,728.4, respectively); these peaked at day 28 and decreased rapidly in the following months.

“The recombinant adenovirus type-5 vector-based Ebola vaccine was safe and highly immunogenic in healthy Sierra Leonean adults, and 8.0 × 1010 viral particles was the optimal dose,” the authors write.

Two authors are employees of Tianjin CanSino Biotechnology, a co-developer of the vaccine.

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