coronavirus August 2, 2021 3:25 pm Interview: UCSF Doctor Talks Breakthrough Cases, Mask Mandate UCSF infectious disease specialist Dr. Peter Chin-Hong details the science behind COVID-19 breakthrough cases and what the new mask mandate can do for case rates. US & World Videos 4:02 Updated COVID vaccines coming 3:12 California experiencing COVID summer surge 1:58 COVID summer surge: CDC data shows cases ‘very high' in California 2:23 Bay Area COVID-19 levels on the rise this summer 2:27 Summer surge? South Bay health officials keep close eye on COVID-19 concentrations