Do masks really protect us? Are children less vulnerable to COVID-19? And why do scientists hope you avoid indoor bars? This week, GZERO World is taking all of our burning questions about the latest in the pandemic to a Harvard epidemiologist. Marc Lipsitch is a Professor in the Department of Epidemiology at the Harvard T.H. Chan School of Public Health and the Director of the Center for Communicable Disease Dynamics. So, he knows his stuff!