In 25 states, the District of Columbia and Guam, more than half of adults are now fully vaccinated against COVID-19, according to the latest CDC data. New England leads the U.S. in vaccination rates among adults. Maine, Connecticut and Vermont have the highest vaccination rates among adults, with more than 62% of residents age 18 and over fully vaccinated. … The states with the lowest rates of fully vaccinated adults are in the South. In Mississippi, Alabama, Arkansas, Tennessee, Louisiana and Georgia, fewer than 40% of adults are fully vaccinated.