The number of U.S. children fully vaccinated against potentially deadly diseases such as diphtheria and measles had been slipping before 2011. Since then, national declines have slowed or even reversed. Rates for kindergartners are noticeably higher than for children 19 to 35 months old because of state laws requiring them to have the full series of inoculations before they can enter the classroom. The laws vary, “but overall they say, 'We have to protect our children.' It's terrific,” says William Schaffner, professor of preventive medicine at Vanderbilt University. Vigilance remains needed, however; levels have eroded slightly for the older group. That may be because laws in some states do not require the entire series of recommended doses or allow parents to easily obtain exemptions. Young parents may seek to opt out because they do not think diseases are serious and may not have learned about them in middle or high school health classes, which tend to focus on subjects such as sexual activity and drug use.

How Many Doses?

The U.S. Centers for Disease Control and Prevention recommends four doses of DTaP vaccine and one dose of MMR vaccine by the time children are 19 to 35 months old. It recommends five doses of DTaP and two of MMR by ages four to six, which is what most states require for school entry. Data below are for these levels (graph on left).

No More Exemptions

Some parents are determined to skirt kindergarten immunization laws, which can pull down a state's average. In 2016, when California ended exemptions based on a parent's religious or philosophical beliefs, medical exemptions—authorized by doctors or forged in their names—tripled, compared with 2015 (graph on right).

Credit: Jan Willem Tulp; Source: Centers for Disease Control and Prevention