In September, New York City declared that its latest measles outbreak was over. More than 60 percent of the 650 people who contracted the illness were children under 5, those most susceptible to a severe measles illness.

To prevent future outbreaks, we have to figure out what caused the last one. The problem is that we are misdirecting our attention. Much of it is focused on the global anti-vaccine movement.

But there is a much larger group: the “vaccine hesitant.” These people intentionally delay or deviate from the routine schedule, staggering vaccine administration according to their own timeline. This leaves children without adequate protection from preventable diseases and puts their community at risk for outbreaks. And it’s unscientific.

A committee of experts known as the Advisory Committee on Immunization Practices annually recommends an evidence-based schedule for every vaccination to the Centers for Disease Control and Prevention. No other schedule for any vaccine provides better safety or efficacy. (For measles, it’s one shot when the baby is around 12 to 15 months old and another shot at 4 to 6 years. If there is an outbreak, infants who live in that area should get a shot starting at 6 months and then continue with the standard regimen.)