is main interests are in the epidemiology, prevention and control of important non-communicable diseases, and the development of primary care in China.

During the COVID-19 pandemic, KK was among the first researchers in western countries who advocated the importance of mask wearing in the community to control the pandemic on 2 March 2020. He questioned the guidance of the WHO on masks in the BMJ on 11 March and published a Comment summarising the importance of masks in The Lancet on 16 April. These have informed the debate on the issue, which culminated in the changes in national guidance in the US, Canada, the UK as well as that of the WHO.