I am currently Assistant Professor at the School of Public Health, The University of Hong Kong. My research focuses on the epidemiology of respiratory virus infections, and I lead large-scale community-based longitudinal observational cohorts and randomised trials on vaccine immunogenicity and efficacy, individual and population immunity, transmission and burden of influenza and COVID-19. Lately I am interested in causal inference analyses, supported by my training as Takemi Fellow in International Health at Harvard T. H. Chan School of Public Health. I have taken various leadership roles in the field, and featured as one of the “Five science stars making their mark in China” by Nature Index. I was a co-Chair for a WHO technical advisory group on developing an online tool for member states to assess and reduce COVID-19 airborne transmission risks indoors (ARIA), and a member of the WHO advisory group on redefining the terminology for through-the-air transmission of pathogens (TTAT). I currently serve as an Editor for the International Journal of Epidemiology (IJE), and a popularly elected Council member of the International Society for Influenza and other Respiratory Virus Diseases (ISIRV), one of the largest international societies on respiratory virus research.With 10+ years of experience in international collaborative research, including funding support from NIH R01/U01 and US CDC, I publish and present regularly in peer-reviewed journals and international conferences (h-index 18 from 3,640+ citations, and 2 Highly Cited Papers in Field). I review journal articles and grant proposals: for academic journals across multiple disciplines such as BMJ, JAMA, Lancet Microbe, Science Translational Medicine, Nature Reviews Microbiology and BMJ Global Health; and funding agencies including the UK Medical Research Council and Wellcome Trust. I have completed comprehensive research training in the epidemiology (PhD) and virology/immunology (MPhil) of human respiratory virus infections. I teach epidemiology for MPH and research postgraduates (class size 220+), problem-based learning (PBL) for medical students and examine external PhD theses.ORCID: https://orcid.org/0000-0001-7314-840X