Has the seven-valent pneumococcal conjugate vaccine had an impact on invasive pneumococcal disease in Western Australia?

Enhanced surveillance for invasive pneumococcal disease (IPD) has been ongoing in Western Australia since 1996. We describe the epidemiology of invasive pneumococcal disease in children aged <2 years between 1996 and 2005. Pneumococcal conjugate vaccine has been offered to Aboriginal children and other high-risk children since July 2001 and to all Australian children since January 2005. A total of 1655 IPD cases were reported of whom 361 (55 Aboriginal) were aged <2 years. From 1996-2001 to 2002-2005, IPD incidence declined from 192 to 124/100,000/annum in Aboriginal children and from 70 to 56/100,000/annum in non-Aboriginal children. Incidence of IPD due to vaccine serotypes (VT) declined from 118 to 43/100,000/annum (p=0.05) in Aboriginal children and from 59 to 45/100,000/annum in non-Aboriginal children (p<0.001), with no increased incidence of disease due to non-vaccine serotypes. Continued surveillance is essential to measure the impact of the childhood pneumococcal conjugate vaccination program on IPD incidence and to identify the emergence of disease due to non-vaccine serotypes.