New COVID-19 Vaccine Shows Promise in Phase 1/2 Trial

An inactivated SARS-CoV-2 vaccine can induce humoral responses in children, according to new data. Neutralizing antibody titers produced by the 3.0-μg dose were higher than those produced by the 1.5-μg dose.

To assess the safety, tolerability, and immunogenicity against COVID-19 of the CoronaVac vaccine, which contains inactivated SARS-CoV-2, the researchers conducted a double-blind randomized, controlled, phase 1/2 clinical trial of the vaccine in a group of healthy participants whose ages ranged from 3 to 17 years and who had no history of SARS CoV-2 exposure or infection.

The phase-1 leg of the trial enrolled 72 participants between October 31 and December 2, 2020, and the phase-2 leg enrolled 480 participants between December 12 and December 30, 2020. All participants came from the Hebei Provincial Center for Disease Control and Prevention in Zanhuang, China.

Doses of vaccine in 0.5 mL of aluminum hydroxide adjuvant or control doses of adjuvant alone were given on days 0 and 28 of the trials. In the phase-1 leg, participants were divided into 2 blocks with doses of either 1.5 μg or 3 μg per injection. In the phase-2 leg, participants were randomly assigned to either CoronaVac, 1.5 μg or 3 μg per injection, or adjuvant only in a 2:2:1 ratio.  

The primary safety endpoint was adverse reactions within 28 days after each injection in all participants who got at least 1 injection, and the primary immunogenicity endpoint was the seroconversion rate of neutralizing antibody to live SARS-CoV-2, 28 days after the second dose.

The researchers found no significant difference between the vaccine groups and the control group in the rate of adverse reactions (p = 0.55). Most were injection site reactions and were mild or moderate in severity. Seroconversion to neutralizing antibodies occurred in all participants after the second dose in both dose groups in phase 1 and in 97% in the lower-dose group and all participants in the higher dose group in phase 2.  

“The results support the use of the 3.0-μg dose with a two-immunisation schedule for further studies in children and adolescents,” the researchers concluded.

—Ellen Kurek

Reference
Han B, Song Y, Li C, et al. Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy children and adolescents: a double-blind, randomised, controlled, phase 1/2 clinical trial. Lancet Infect Dis. 2021;21(12):1645-1653. https://doi.org/10.1016/s1473-3099(21)00319-4