COVID-19 initiated by a zoonotic event has become the worst pandemic in the past 100 years. The ongoing pandemic is likely to be followed by an endemic disease. There is an urgent need to better understand this disease in both pandemic and epidemic forms to inform public health policy. This proposal aims at using multidisciplinary research approaches including virology, immunology, biotechnology, vaccinology, epidemiology, bioinformatics and big data analysis, to study two key research questions. Firstly, we will genetically and phenotypically characterize a panel of SARS-CoV-2 isolates found in Hong Kong and abroad. Secondly, we will study the immune responses triggered by COVID-19 and its vaccines. Our long-term goal is to use our findings to provide evidence-based options for the control of this pandemic and its aftermath.