Invasive pneumococcal infections in Canadian children, 1991-1998: Implications for new vaccination strategies

We reviewed 2040 consecutive cases of invasive pneumococcal infection that were seen at 11 pediatric centers across Canada during 1991-1998 to determi ne if such infections could be prevented by new conjugate vaccines. Isolate s from 1528 cases were serotyped, Most cases (61.5%) occurred in patients a ged >2 years, Underlying medical conditions were present in 23.2% of case p atients. Serotypes in the 7-valent conjugate vaccine matched isolates as fo llows: 85.8% of tested isolates from children aged 6 months to 5 years, but significantly fewer isolates in younger and older children; 72.7% of isola tes from non-healthy children, but 83.9% of isolates from previously health y children; and 95.4% of isolates with high-level penicillin resistance, bu t only 72.7% of those with intermediate-level resistance. Significant natur al variation in the proportion of isolates matching 7-valent vaccines occur red from year to year and among centers. New conjugate vaccines have great potential but their effectiveness and limitations require ongoing study.