Antibody levels in people inoculated with CanSino Biologics' (CanSinoBio) single-dose Covid-19 vaccine fell by some 30 percent after six months, however, a booster shot could offer a significant lift, a senior executive said late on Thursday.

The decline in antibodies does not necessarily mean the shots will lose their protection, though how fast they wane could still serve as an important indicator of the immune response, Zhu Tao, chief scientific officer at China's CanSinoBio, said in an online presentation...