Wear your mask. Or, don't wear your mask if you are vaccinated, as long as you are outside. But, keep masking and social distancing inside even if you are vaccinated. It's confusing to many. Vaccines have been proven to prevent serious infection, and studies that show a reduction in transmission are building, but they aren't foolproof. A recent study by Public Health England found that a single dose of either the Pfizer-BioNTech or AstraZeneca vaccine reduced household transmission by up to half. Those both require two doses to be considered "fully vaccinated." The study comes as we hear more about breakthrough COVID cases. In this episode, Colleen Kelley, MD, an associate professor of infectious diseases at Emory University School of Medicine in Atlanta and a principal investigator for the Moderna and Novavax phase III clinical trials at the Ponce de Leon Clinical Research Site, joins us to explain the risk of transmission after vaccination.