Objective: We examined the relationship between early and exclusive continuity of care at the initial source of care and immunization coverage.
Methods: We used a cohort study design with 641 randomly selected children initiating care before 3 months and making 2 or more visits to an inner-city practice network. We used 2 complementary data sources: medical records and the New York City Department of Health Citywide Immunization Registry. Immunization measures were cumulative age appropriate and up-to-date at 18 months (UTD18).
Results: There was a gradual attrition from the initial source of care. By 18 months, less than half the children (46%) remained in care. Regardless of continuity, nearly half (42%) had used other immunization providers. The initial source of care contributed most immunizations (89%-94%); however, across all levels of continuity, children who also used other providers had higher immunization rates. We found a threshold effect of continuity beginning at 12 months: children in care from 12 to 14 months were 17.5 times more likely to be UTD18 than those in care less than 6 months. Each additional period in care increased the time remaining current with immunizations. Among children UTD18, 88% were in care at 11 months compared with 38% among those not UTD18, a 50% difference.
Conclusions: Continuity of care at the initial source of care had a significant and lasting impact on immunization coverage, even if not used exclusively. Interventions promoting continued use of the medical home over the first 2 years of life may help improve immunization coverage.