Medicaid managed care in New York: problems and promise for childhood immunizations.

New York State is aggressively pursuing mandatory Medicaid managed care. Under managed care, physicians and plans have a defined population for which they are responsible, quality assurance monitoring emphasizes immunization rates along with other preventive services, and population-based incentives are possible. The literature does not offer compelling evidence, however, that immunization coverage is any better in managed care than under fee-for-service. If reimbursement is low and physician capacity insufficient, immunization rates may be considerably worse. In New York, care needs to be taken so that expansion does not outstrip the capacity of managed care plans to absorb additional enrollees.