According to a recent study of surveillance data from the Vaccine Safety Datalink published in this journal, 48.7% of children were undervaccinated at some time prior to their second birthday and 1 in 8 were undervaccinated owing to parental choice to delay or refuse certain vaccines.1 Undervaccination has been attributed to access to health care services and missed opportunities. Now, however, it has become increasingly evident that it is the result of vaccine hesitancy as parents question the need for certain vaccines and request alternate schedules.