Epidemiology of invasive pneumococcal disease in Southern California: Implications for the design and conduct of a pneumococcal conjugate vaccine efficacy trial

Population-based prospective surveillance of invasive pneumococcal disease was done in Southern California from 31 March 1992 to 1 April 1995; 814 cases were identified, for an incidence of 12.5/100,000 persons/year. The incidence among persons less than or equal to 2, less than or equal to 5, and greater than or equal to 65 years of age was 145, 72, and 32/100,000, respectively, More than 95% of cases included bacteremia; incidence of meningitis was 0.8/100,000, Among children less than or equal to 2 years of age, 79% of isolates were obtained in the outpatient setting, compared with 16% of isolates among persons greater than or equal to 15 fears of age, Eighty percent of isolates were serotypes included in heptavalent pneumococcal conjugate vaccines currently being evaluated. Children less than or equal to 2 years of age were at highest risk of having an isolate resistant to penicillin. Among resistant isolates, high-level resistance increased from 4% to 21% over a 3-year period, Prospective epidemiologic data are needed to perform a protective efficacy trial of pneumococcal conjugate vaccines in infants, among whom most invasive pneumococcal disease is vaccine-preventable.