Safety and immunogenicity of a recombinant adenovirus type-5-vectored COVID-19 vaccine with a homologous prime-boost regimen in healthy participants aged 6 years and above: A randomized, double-blind, placebo-controlled, phase 2b trial

Clinical Infectious DiseasesZhu F, Jin P, Zhu T, et al. | September 24, 2021


In children and adolescents aged 6-17 years, administration of a single dose of adenovirus type-5 (Ad5)-vectored COVID-19 vaccine resulted in induction of robust immune responses safely.

  • A randomized, double-blind, placebo-controlled trial.

  • A total of 430 participants were enrolled and administered low-dose vaccine, middle-dose vaccine or placebo.

  • Thirty participants were aged 18-55 years (MID cohort), 250 participants aged 56 years and older (OLD cohort), and 150 participants aged 6-17 years (MIN cohort).

  • Significant RBD-specific ELISA antibodies were induced after receipt of Ad5-vectored COVID-19 vaccine, which decreased with increasing age.

  • In children and adolescents, higher antibody responses were elicited after receiving a single dose when compared with that elicited in adults following two doses.

  • Homologous prime-boost vaccination was identified as safe and tolerable.

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