Sinovac Biotech (Sinovac), a vaccine maker in China, has said it plans to start a clinical trial of its experimental COVID-19 vaccine, CoronaVac, with children and adolescents later this month, widening its test on a shot that's already in the final stage of study with adults, Reuters news agency reported on Thursday.

According to a registration record published on 16 September 2020, a total of 552 healthy participants aged between three and 17 will take two doses of US-listed Sinovac's CoronaVac, or a placebo, in a combined Phase 1 and Phase 2 trial estimated to begin on 28 September 2020, in the northern Chinese province of Hebei.

Reportedly, this trial has already been approved by the Chinese regulator.

According to Reuters, China has inoculated at least tens of thousands of its citizens rolling out experimental COVID-19 vaccines, attracting international interest in their development, despite expert concerns over the safety of drugs that have not completed standard testing.

As a part of that programme, CoronaVac, being tested in final-stage large-scale trials in Brazil, Indonesia and Turkey, has already been given to about 90% of the company's employees and their families.

The World Health Organisation in that regions has reported that data so far suggests the virus generally causes milder disease in children compared with adults, but some cases of children requiring intensive care have been also reported,

Sinovac had said that CoronaVac appeared to be safe and able to induce antibodies for older people, while the vaccine-generated antibody levels were slightly lower than seen in younger adults, citing preliminary results from an early to mid-stage trial.