Trends in invasive Haemophilus influenzae type B disease in Australia, 1995-2005

The epidemiology of invasive Haemophilus influenzae type b (Hib) disease and its prevention by vaccination is reviewed for the period 1995 to 2005, comparing surveillance data for 1995-2000, when both PRP-OMP and HbOC vaccines were used, with 2000-2005, when only PRP-OMP vaccine was used. Over the whole time period, notifications of invasive Hib disease have declined dramatically. In the second time period, a greater decline in Hib cases was seen. This could be due to either the different vaccines being used, differences in vaccine coverage or both. Although disease incidence has decreased markedly in both Indigenous and non-Indigenous populations, Indigenous people are still at significantly greater risk. It is also concerning that almost 60% of invasive Hib cases in children are preventable, in that they are occurring in unimmunised or incompletely immunised children among whom the incidence of Hib disease is estimated to be about 15 times that of fully immunised children. Australia is now in the third era of Hib vaccine use, during which both PRP-T and PRP-OMP vaccines are used, depending on ethnicity or jurisdiction of residence. Continued enhanced surveillance for invasive Hib disease is important for optimal monitoring of trends into the future.