Dr. Ryan Au Yeung, an assistant professor at the School of Public Health at the University of Hong Kong, discusses his research on the relationship between smoking and the risk of contracting COVID-19. Using a method called Mendelian randomization, the study analyzes genetic data to determine causality. The research found that people who smoke have a higher risk of contracting COVID-19, including mild cases. The results suggest that quitting smoking is an effective way to reduce the risk of COVID-19.