The nation's youngest children are getting their chance at vaccines for COVID-19.Shots began Monday at a few locations, and hospitals in the nation's capital, Los Angeles, New York and Seattle were among those to offer the vaccine on Tuesday. The Food and Drug Administration cleared vaccines from Moderna and Pfizer last week and the Centers for Disease Control and Prevention gave the final signoff over the weekend. Roughly 18 million youngsters under 5 are eligible. For the little kids, Pfizer's vaccine is three shots and Moderna's is two shots. Getting some parents on board may be a challenge given low vaccination rates in school-age kids.