Table 29 provides measures of morbidity for comparison of disease burden relevant to current general or targeted programs. For most vaccine preventable diseases, the notification and hospitalisation rates are highest in children under five years of age. Immunisation programs targeting this age group are probably nearing their highest practically achievable targets, as measured by the Australian Childhood Immunisation Register and supported by a range of parent and provider incentives.41,296,308,309 For other vaccine preventable diseases, there is either a greater disease burden in older age groups, such as hepatitis A and B, pertussis (although rates in infants remain high) and tetanus, or important secondary age peaks in young adults, for diseases such as measles, mumps and meningococcal disease.
With respect to immunisation programs targeting diseases currently included in the NIP schedule, measles, mumps, meningococcal disease and pertussis in older teenagers and young adults remain priorities. Australia has so far not found a successful means to deliver vaccination programs to older adolescents and young adults no longer attending school, with the approaches adopted for the promotion of MMR and meningococcal C vaccines in this age group having relatively little impact. School-based delivery of conjugate meningococcal C and adult-formulated pertussis vaccines has been a success and provides a model for other interventions in educational institutions. Delivery of vaccines such as MMR, pertussis and meningococcal C to young adults is difficult to implement and it is likely that this group will represent an ongoing challenge for control of measles, mumps, rubella, pertussis and meningococcal C over the next few years. The 2003 addition to the ASVS of dTpa for adolescents in Australia demonstrated an international lead in pertussis control, which should be mirrored in notifications, provided high coverage is maintained. Australia is now in the mature phase of control for many vaccine preventable diseases, where incidence is very low and effectively close to elimination. Vaccines against diseases such as human papillomavirus and rotavirus will be implemented in the near future. Evaluation of the impacts of these new programs, as well as continued efforts to maintain current programs, will be required to sustain the success of immunisation in Australia over the coming years.