The source of the organism is the upper respiratory tract. Immunisation with a protein conjugate vaccine reduces the frequency of asymptomatic colonisation by Hib. Before the introduction of the vaccine, Hib was the most common cause of bacterial meningitis in children. Worldwide immunisation coverage is increasing, with approximately 184 countries having introduced Hib onto their schedules by the end of 2012 (this includes four countries that have introduced Hib in part of the country), or 96 percent of all 191 WHO member states.1
Hib vaccine was introduced in 1994 (see Appendix 1). In 1993, 101 children aged under 5 years had laboratory-confirmed invasive Hib disease (an age-specific rate of 36.4 per 100,000 population). By 1999 only five children in this age group had laboratory-confirmed disease (1.7 per 100,000) (Figure 6.1).
Source: Institute of Environmental Science and Research
From 2000 to 2012, 54 laboratory-confirmed cases of invasive Hib were reported in children aged under 5 years.2 Of the 54 cases, nine were reported as having received Hib immunisation appropriate for their age and 41 had either received no Hib immunisation or were incompletely immunised for their age. The immunisation history of the remaining four cases was unknown. There were no laboratory-confirmed cases of invasive Hib in children aged under 5 years in 2013.
In summary, of the small number of children who have developed Hib infection in New Zealand since the Schedule change in 2000 (see Appendix 1, section A1.3.2), most had either received no Hib vaccines or were incompletely vaccinated for their age.