Whether children receive a dose of a Covid-19 vaccine often depends on where they call home. About 81 percent of children ages 12 to 17 in Vermont have had at least one dose of a vaccine to protect against Covid-19, according to data from the CDC analyzed by NBC News. Puerto Rico leads the U.S. with a vaccination rate of 91 percent. But in West Virginia, the rate is just 35 percent — a marker of stark regional disparities that are deepening across the country.