President Trump’s plan for reopening the country’s economy uses a three-phase approach, relies on data, and defers to governors to reopen their own states. Epidemiologists say that’s all good. But one thing it doesn’t do is provide any mechanism to re-impose restrictions if the virus resurges. Marco Werman gets reaction to the president’s plan from Marc Lipsitch, an epidemiologist and director of the Center for Communicable Disease Dynamics at the Harvard T.H. Chan School of Public Health.