CoronaVac Safe, Triggers Strong Antibody Response in Children and Adolescents

CoronaVac, a COVID-19 vaccine developed by the Chinese biopharmaceutical company Sinovac, has shown to be safe and generate a strong antibody response in children and adolescents following 2 doses in a recent trial.

Results from the study were published in the journal The Lancet Infectious Diseases.

“Herd immunity against COVID-19 is the prerequisite to end this pandemic, either through vaccinations or natural infection. Most estimates placed the threshold at 65-70% of the population gaining immunity, mainly by vaccination,” Bin Cao, vice president and director of Respiratory and Critical Care Medicine at the China-Japan Friendship Hospital said. “However, widely circulating virus variants and persistent hesitancy on vaccine make this threshold difficult to reach. Thus, the calculation has to be revised upward and children must be covered in the immunization campaign.”

The double-blind, randomized, controlled, phase 1/2 clinical trial included 550 participants between the ages of 3 and 17 years old who received at least 1 dose of the CoronaVac vaccine or alum only.

The phase 1 part of the trial was an age de-escalation in three groups and dose-escalation in two blocks (1·5 μg or 3·0 μg per injection). Each block saw participants randomly assigned (3:1) by means of block randomization to receive CoronaVac or alum only.

In the phase 2 part of the study participants were randomly assigned (2:2:1) by means of block randomization to receive either CoronaVac at 1·5 μg or 3·0 μg per dose, or alum only.

Findings from the study demonstrated that 100% of participants in both the 1.5µg and 3µg groups (27/27 and 26/26 participants, respectively) generated antibodies against SARS-CoV-2 in the phase 1 trial. In phase 2, 97% (180/186) of participants in the 1.5µg group produced antibodies against SARS-CoV-2, compared with 100% (180/180 participants) in the 3µg group.

Additionally, in both phases of the trial the participants receiving 3µg of the vaccine produced a stronger immune response in comparison to those in the 1.5µg group.

Adverse reactions within 28 days occurred in 56 (26%) of 219 participants in the 1.5µg group, 63 (29%) of 217 in the 3µg group, and 27 (24%) of 114 in the control group.

“Children and adolescents with COVID-19 usually have mild or asymptomatic infections compared with adults; however, a small number may still be at risk of severe illness. They can also transmit the virus to others, making it vital to test the safety and effectiveness of COVID-19 vaccines in younger age groups,” Quian Gao, vice president of research & development for Sinovac said. “Our finding that CoronaVac was well tolerated and induced strong immune responses is very encouraging, and suggests that further studies in other regions, involving larger, multi-ethnic populations, could provide valuable data to inform immunization strategies involving children and adolescents.”