The results were from early and mid-stage clinical trials with over 550 subjects, said Geng Zeng, the medical director at Sinovac, at a press conference.

While the vaccine has already been allowed for use in adults in China, further testing was needed to see how it would work with children.

More than 70 million shots of Sinovac’s vaccine has been given worldwide, including in China.

There were two instances of high fevers in response to the vaccine during trials, one in a 3-year old participant and the other in a six-year old. The rest of the participants had experienced mild symptoms, said Geng.

State-owned Sinopharm, who has two COVID-19 vaccines, is also investigating the effectiveness of its vaccines in children. They had said in January that they submitted clinical data to regulators, though it was unclear if it was for both of their shots or just one.