Delays in the primary vaccination of children.

The results of a population-based survey of 170 children's vaccination records were used to calculate the cumulative distributions of the ages (in months) at which each dose of vaccine had been received. Considerable delays in the administration of measles-mumps-rubella (MMR) vaccine and of the fourth dose of diphtheria-pertussis-tetanus vaccine were observed, particularly in children vaccinated by private physicians rather than at public health clinics. The delay before MMR vaccination causes concern because of the frequency of measles in children aged 1 to 2 years, particularly those attending day-care centres, and the fragility of the herd immunity against this disease. Physicians should follow up patients who have missed appointments for MMR vaccination if a voluntary measles control program is to succeed.