Beijing, Jun 29 (IANS): 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.

China earlier this month, authorised the emergency use of CoronaVac, for children aged between 3 and 17 year.

In a randomised controlled trial of 550 young people, the vaccine manufactured by Chinese company Sinovac, more than 96 per cent children and adolescents developed antibodies against SARS-CoV-2, the virus causing Covid-19.

Most adverse reactions were mild or moderate, with pain at the injection site the most commonly reported symptom.

"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 of CoronaVac in 550 healthy children and adolescents aged 3-17 years in Zanhuang County, China between October 31 and December 30.

The vaccine (either 1.5 or 3 microgram per dose) or a control was given by intramuscular injection in two doses, at day 0 and day 28.

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.

"Owing to the small number of participants in the study, the results should be interpreted with caution as it was not possible to draw strong statistical conclusions," the researchers said.

"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," Gao said.

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.