Vaccination levels in Los Angeles public health centers: the contribution of missed opportunities to vaccinate and other factors.

We abstracted 752 randomly selected records of 2-year-old children at 5 public health centers in Los Angeles. Only 27% of the children were up-to-date in their vaccinations by 2 years of age. Being up-to-date was strongly associated with the number of missed opportunities to vaccinate and number of well child visits. Missed opportunities to vaccinate occurred during 52% of all visits and were associated with minor illness diagnoses and inaccurate immunization status assessment by nurses. Frequent missed opportunities to vaccinate and inadequate numbers of well child visits may result in low immunization levels among children attending public health clinics.