Coronavirus: signs of immunity boost from third Sinovac shot, study finds
- China’s CoronaVac was used in a study looking at how and when a booster shot might further protect against Covid-19
- Researchers said factors such as testing and lab methods made it difficult to directly compare the CoronaVac results with those of other vaccines
Since May last year researchers, including Yu Hongjie with Fudan University’s school of public health, and Zhu Fengcai, deputy director of Jiangsu Centre for Disease Control and Prevention, have tested the immunogenicity – the ability of cells or tissues to provoke an immune response – of Sinovac’s CoronaVac vaccine, of which 3.73 billion doses have been administered worldwide. It is one of the two vaccines rolled out in Hong Kong.
They are investigating how long CoronaVac induces immunity, whether a booster shot will be needed and, if so, the optimal timing of the booster.
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Participants were randomly assigned to groups and administered two doses either 14 days or 28 days apart. Each group was either administered a 3 microgram dose, a higher 6 microgram dose or a placebo. Four weeks later, higher concentrations of antibodies were found among those who been vaccinated with a longer spacing between doses.