BEIJING - CanSino Biologics' (CanSinoBIO) single-dose Covid-19 vaccine, given at a lower dosage than that for adults, is safe and triggers an immune response in children aged six to 17, results from a small trial showed.
Researchers decided to lower the dosage after a few participants developed fever and headaches graded at level two severity - the second-lowest of four levels.
In children, the lower dose triggered higher antibody levels than the dosage approved for use in adults in China, according to the peer-reviewed finding from a mid-stage trial.
The trial recruited 150 children and around 300 adults.
The results also showed that children given one lower dose had a stronger antibody response than adults who were given a booster shot 56 days after the first dose.
But the antibody readings did not show to what extent the vaccine can offer protection against Covid-19, researchers from a Chinese disease control agency, CanSinoBIO and other Chinese institutes cautioned in a paper.
CanSinoBIO's vaccine has not yet received the green light for children.
China has approved two vaccines, developed by Sinovac and Sinopharm, for use in children from the age of three but vaccinations have yet to begin for those under 12.
The paper said the booster shot for CanSinoBIO's vaccine improved antibody responses in participants of different age groups, especially for older adults.
But cellular responses, another important part of the human immune system, were not boosted by the second shot and researchers said a wider interval than 56 days should be considered.