Two doses of China’s Sinovac vaccine offered older people only a moderately high level of protection against severe disease and death from Covid-19, but a third dose significantly bolstered their defenses, according to a new study by scientists in Hong Kong.
The study, based on patients infected during the current devastating Omicron wave in Hong Kong, serves as a cautionary note for mainland China, where Sinovac is a pillar of the country’s vaccination program. Many older people there have yet to receive booster shots.