The epidemiology of invasive pneumococcal disease in children in Far North Queensland

Objectives: To describe the epidemiology of invasive pneumococcal disease in children under 5 years of age in Far North Queensland and to examine the potential impact of a seven- and 11-valent conjugate pneumococcal vaccine. Methods: A review of all cases of invasive pneumococcal disease in children under 5 years of age in Far North Queensland over a 9 year period (1992-2000). The distribution of the serotypes of isolates causing invasive pneumococcal disease was compared with the serotypes contained in the two vaccines. Results: The annual incidence in indigenous and non-indigenous children under 5 years of age was 163 (95% confidence interval (CI) 122-213) and 42 (95% CI 31-55) cases per 100 000 children, respectively. For children under 2 years of age, these figures were 297 (95% CI 208-411) and 71 (95% CI 49-100), respectively. There was a greater variety of serotypes isolated from indigenous children (n = 17) than from non-indigenous children (n = 9; P < 0.01). The serotypes within the seven-valent vaccine accounted for 62% (95% CI 46-75%) and 88% (95% CI 76-95%) of the isolates from indigenous and non-indigenous children, respectively (P < 0.01). Serotypes within the 11-valent vaccine accounted for 72% (95% CI 57-84%) of the isolates from indigenous children under 5 years of age, but did not account for any extra isolates from non-indigenous children. Conclusion: Although the seven- and 11-valent conjugate pneumococcal vaccines cover only approximately 60 and 70%, respectively, of the isolates that cause invasive disease in indigenous children in Far North Queensland, they nevertheless have the potential to prevent much morbidity in and hospitalization of these children. It will be essential to maintain surveillance following the introduction of conjugate pneumococcal vaccines so as to monitor changes in the incidence of invasive pneumococcal disease, particularly in high-risk children.