Mask guidance for vaccinated covers 46% of Mich. population Lansing — Nearly half of Michigan residents live in counties where the federal government is urging the fully vaccinated to wear masks in public indoor settings because transmission of the coronavirus is “high” or “substantial.” The guidance affected 33 counties as of Monday — including large ones such as Oakland, Macomb and Ingham — up from 10 mostly small, rural counties when the Centers for Disease Control and Prevention’s recommendations were issued nearly a week ago. The counties are home to more than 4.5 million residents, 46% of the state’s population. Michigan’s seven-day average of new COVID-19 cases was 678 on Saturday, an increase from 241 two weeks before. The case rate, 76.8 per 100,000 people, was lower than in all but four states based on data compiled by Johns Hopkins University.