By Holly Yan, CNN Updated 3:29 AM ET, Mon July 20, 2020   (CNN)First, health officials said we shouldn't wear face masks. Then, they said we should. Now, many are saying we must wear masks if we want to protect the economy,  reopen more schools,  and save tens of thousands of lives.   "If we all wore face coverings for the next four, six, eight, 12 weeks across the nation, this virus transmission would stop,"  said Dr. Robert Redfield, director of the Centers for Disease Co