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BACKGROUND: Pneumococcal disease (PD) is a major cause of morbidity and mortality, particularly among young children and the elderly. A 7-valent pneumococcal conjugate vaccine (PCV7) was recommended for routine use in children aged 2–23 months in 2000 and children aged 2–59 months in 2007. In 2010, a 13-valent pneumococcal vaccine (PCV13) was recommended for routine use in children aged 2–59 months. Our objective was to describe PD hospitalizations in California during 1990–2011, the period prior to and during the introductions of PCV7 and PCV13.
METHODS: The California Office of Statewide Health Planning and Development Patient Discharge Database comprises records for each inpatient discharged from non-federal California licensed hospitals. ICD-9-CM diagnosis codes were used to identify and hierarchically categorize patients hospitalized with 1) pneumococcal meningitis (320.2), 2) pneumococcal pneumonia (481), and 3) pneumococcal septicemia without focus (038.2) during 1990–2011. Rates per 100,000 were calculated by age group (<1, 1–4, 5–17, 18–64, and ≥65). Significant trends and changes in trends were identified using Joinpoint Regression Program v3.5.4 (National Cancer Institute, Bethesda, MD).
RESULTS: The rate of PD hospitalizations decreased from 31.7 in 1990 to 13.6 in 2011 (p-value<0.001). The largest decrease occurred during 1997–2004 (31.0 to 15.2; p-value<0.001). Decreases (p-values≤0.001) were greatest among infants <1 (52.2 to 18.5 during 1998–2003), children 1–4 (17.7 to 7.5 during 1999–2003), and adults ≥65 (151.3 to 80.0 during 1998–2002). Pneumococcal meningitis and pneumonia hospitalizations also decreased during 1990–2011, with significant decreases during 2003–2011 for meningitis (0.5 to 0.4) and 1997–2004 for pneumonia (27.2 to 13.0). Septicemia hospitalizations decreased during 1998–2004 (3.0 to 1.7; p-value<0.001) but increased during 2004–2011 (1.7 to 2.3; p-value<0.001); this increase only occurred among adults 18–64 (1.2 to 1.6; p-value=0.005), and ≥65 (6.9 to 9.0; p-value=0.03).
CONCLUSIONS: PD hospitalization rates in California significantly decreased during the time period that includes the introduction of PCV7; however, pneumococcal septicemia hospitalization rates increased during 2004–2011 in age groups not routinely recommended to receive PCV7 or PCV13. This analysis is limited by its ecologic study design, the lack of information regarding circulating pneumococcal serotypes in California, and insufficient data to identify trends after PCV13 licensure. Increases in pneumococcal septicemia after pneumococcal conjugate vaccine licensure have not been previously reported and information is needed to determine if these increases are due to serotype replacement or other causes.