The director of the Centers for Disease Control and Prevention told governors last week to prepare for the "large-scale" distribution of a coronavirus vaccine by Nov. 1, according to a letter obtained Wednesday by NBC News. In the Aug. 27 letter, the director, Dr. Robert Redfield, said the CDC had contracted with a pharmaceutical company, McKesson Corp., to potentially distribute hundreds of millions of vaccine doses to health departments and medical facilities across the country in the fall.