Invasive pneumococcal disease in Danish children, 1996-2007, prior to the introduction of heptavalent pneumococcal conjugate vaccine.

AIM: The aim of this study was to document the epidemiology, microbiology and outcome of invasive pneumococcal disease (IPD) among children <16 years with quality surveillance data, just prior to the introduction of the heptavalent pneumococcal conjugate vaccine (PCV7) into the Danish routine immunization programme October 2007.

METHODS

Clinical and microbiological records on cases of IPD in children <16 years admitted to Hvidovre Hospital, Denmark 1996-2007, were retrospectively reviewed.

RESULTS

We identified 106 cases of IPD. The annual incidence of IPD was 11 per 100 000 in children <16 years, but considerably higher, 62 per 100 000, in children <2 years. Additionally, of the children with pneumococcal meningitis 86% were <2 years. We observed no fatalities. A total of 10% developed sequelae, but of the patients with pneumococcal meningitis 27% developed sequelae. Nine patients had known risk factors. The Streptococcus pneumoniae serotype was available for 81 cases. Seventy-five percent of the IPD cases in children aged <2 years were caused by one of the serotypes contained within PCV7, compared to only 24% in children >/=2 years.

CONCLUSION

Our data indicate that an estimated 75% of all IPD cases among children <2 years are caused by PCV7 serotypes and might therefore be prevented by PCV7 vaccination.