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

Abstract

Background: 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.

Objectives: 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.

Method: 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.

Results: 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.

Conclusions: 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.