Streptococcus pneumoniae-related illnesses in young children: secular trends and regional variation

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Abstract
Children <2 years old have been targeted for routine pneumococcal conjugate vaccine. Laboratory-confirmed illnesses represent a minority of all medical care utilization for pneumococcal disease. To evaluate trends in medical care utilization for Streptococcus pneumoniae-related illnesses before introduction of pneumococcal conjugate vaccine (1995 to 1999) and to evaluate regional variation in utilization. Retrospective cohort analysis with the use of computerized billing data of children <2 years old enrolled in Tennessee (Medicaid program) and the Rochester, NY area (commercial and Medicaid managed care plans). Secular trends (1995 to 1999) analysis included 316 519 person-years in Tennessee Medicaid. Regional variation (1998 to 1999) analysis included 130 525 person-years in Tennessee and 26 140 and 3184 person-years in commercial and Medicaid plans, respectively, in the Rochester, NY area. From 1995 to 1999 in Tennessee, the net increase in medical care visits was 12% for pneumococcal and nonspecific pneumonia and invasive disease, 11% for otitis media and 11% for other acute respiratory conditions. Analysis of trends indicated that a significant vaccine effect could be detected if utilization rates declined by 32, 9 and 21%, respectively. In the Tennessee Medicaid population, rates of pneumococcal and nonspecific pneumonia and invasive disease were 60% higher than in either the New York Medicaid or the commercial populations. Children with commercial insurance had the highest medical care utilization for otitis media. Geographic variation and large population differences in medical care utilization among children < 2 years old in three study populations suggest that the benefits of vaccination may vary by region and by population. In the Tennessee Medicaid population, temporal trends and year-to-year variability of pneumococcal-related outcomes were observed from 1995 to 1999. In this population a 10% decline in otitis media visits after the introduction of pneumococcal conjugate vaccine could be detected by trend analysis.