Two ongoing issues with obtaining complete vaccination coverage in all children are obtaining timely vaccination and increasing vaccination levels in children from low-income families. In this study, timely vaccination coverage among low-income children increased during the 13-year period for all vaccines except for Haemophilus influenzae type b. There were substantial disparities in vaccination coverage between children from low-income and those not from low-income households. These disparities decreased for every birth cohort in the study period for measles, mumps, rubella; hepatitis B; and varicella vaccines but increased for the diphtheria, tetanus, pertussis vaccine. Further progress in eliminating these disparities will require multifaceted interventions focused on providers, parents, and financing.