Two doses of CoronaVac, a Covid-19 vaccine manufactured by Chinese firm Sinovac, are safe and produce a strong antibody response among children and adolescents aged 3-17 years, according to a results of phase 1/2 clinical trial published in The Lancet Infectious Diseases journal. The randomised controlled trial covered 550 young people. More than 96% of children and adolescents who received two doses of the vaccine, manufactured by Sinovac, developed antibodies against SARS-CoV-2, the virus causing Covid.
Most adverse reactions were mild or moderate, with pain at the injection site the most commonly reported symptom.
China earlier this month, authorised the emergency use of CoronaVac, for children aged between 3 and 17 year.
"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 immunisation strategies involving children and adolescents," said Qiang Gao, of Sinovac Life Sciences Co, China.
The team conducted a randomised, double-blind, controlled phase 1/2 clinical trial between October and December 2020. The vaccine or a control was given by intramuscular injection in two doses (1.5 or 3 micrograms). The vaccine or a control was given by intramuscular injection in two doses, at day 0 and day 28.
In phase 1, 100% of participants in both the 1.5-microgram and 3-microgram groups generated antibodies. Stronger responses were detected among the 3-microgram group. In phase 2, 97% of participants in the 1.5-microgram group produced antibodies, compared with 100% in the 3-microgram group.
Among the 550 participants who received at least one dose of vaccine or the control, adverse reactions mostly mild or moderate, with pain at the injection site occurred within 28 days in 13 per cent, 73/550 participants.
However, one limitation in the study is that T cell responses -- which play an important role in SARS-CoV-2 infections -- were not assessed in the study, said the researchers. Further, the study involved only a small number of participants and all were of Han ethnicity, highlighting a need for larger studies in other regions and involving multi-ethnic populations.
Long-term safety and immune response data were not available, though participants will be followed for at least 1 year.
Meanwhile, in India, the Pune-based Serum Institute of India (SII) will begin clinical trials of Novavax for children starting July. Hyderabad-based Bharat Biotech has also two vaccines that are being tried on children, Covaxin and BBV154, a one-shot nasal vaccine.
ZyCov-D, the Zydus' Covid-19 vaccine has trials on children in the age group 12-18 years was found effective. The vaccines may be available soon.
US pharma major Pfizer has also announced that its vaccine is safe for children above 12 years of age.