In Australia, the endemic transmission of many diseases which caused significant burden in the past, disproportionately affecting Aboriginal and Torres Strait Islander people, has been largely controlled. Diseases like diphtheria, tetanus and poliomyelitis have become rare in Australia due to vaccination programs. There have also been significant declines more recently in diseases like measles, varicella and hepatitis A, which are not, or are no longer, of particular concern in Aboriginal and Torres Strait Islander communities. However, all of these diseases are still endemic in some or many developing countries around the world, and could be easily acquired by travellers or imported by returning travellers, posing a threat to unimmunised individuals. Hence, maintaining high vaccination coverage and improving timeliness of vaccination among both children and adults should remain an important goal for achieving and sustaining the elimination of these diseases.
Although rates of Hib disease have decreased significantly since the introduction of Hib vaccines in 1993, the plateauing in Aboriginal and Torres Strait Islander children, and increasing disparity with other children, are concerning. Continuing Hib nasopharyngeal carriage, increased susceptibility to Hib disease, and poor immune responses to immunisation have been implicated as driving forces behind continuing disease in Aboriginal and Torres Strait Islander children. The progressive withdrawal of PRP-OMP vaccines (3 doses) in Australia from 2005 to 2009, replaced by 4 doses of PRP-T, was due to an international shortage of PRP-OMP vaccine. While it is possible that higher disease rates in young infants could be associated with the later age of protection from PRP-T vaccine, it is also possible that the higher immunogenicity of the PRP-T vaccine will result in reduced Hib carriage. Close monitoring is important to detect any re-emergence of disease as soon as possible.
Some diseases like pertussis have still not been controlled and outbreaks continue to occur. Pertussis is the least well controlled of the diseases that have long-standing, well-established vaccination programs. Of these diseases, pertussis has the highest notification rates (in all age groups) and higher hospitalisation rates. Epidemics continue to occur in Australia which affect both Aboriginal and Torres Strait Islander and other people, although Aboriginal and Torres Strait Islander people have higher hospitalisation rates. In order to protect the most vulnerable in the community from severe disease, from 2008 to 2012, DTPa vaccination was funded by various states and territories for parents/contacts of infants under the ‘cocooning’ strategy. Parents are also now encouraged to have their infant’s first vaccination given at 6 weeks of age, instead of the usual 2 months, and this is being implemented for Aboriginal and Torres Strait Islander as well as other infants. Timely administration of the 4- and 6-month doses is also very important.
Although there have been substantial declines in severe rotavirus disease, mumps, meningococcal disease and hepatitis B infection, the rates are still higher in Aboriginal and Torres Strait Islander people than in other people. The decline in severe rotavirus disease after vaccine introduction was most pronounced in infants <1 year of age, but less marked in Aboriginal and Torres Strait Islander than in other infants. By far the highest hospitalisation rates continue to occur in Northern Territory Aboriginal and Torres Strait Islander children. Vaccination delay is having a substantial impact on coverage for rotavirus vaccine due to the upper age limits for vaccination and this is most marked for the 3-dose schedule. Consideration of the role of age cut-offs and 2-dose versus 3-dose schedules may be necessary. Genotype surveillance is critically important to be able to detect any possible future emergence of genotypes for which there is lower vaccine-derived immunity.
Mumps has been reported to have recently made a re-emergence globally. During this reporting period, a prolonged outbreak was recorded with a peak in hospitalisations in 2007/2008. This outbreak predominantly affected Aboriginal and Torres Strait Islander adolescents and young adults. The rates among Aboriginal and Torres Strait Islander people have declined from the highest of 5 per 100,000 in 2007/2008 to less than 1 per 100,000 in 2009/2010. Whereas mumps was historically a disease of childhood, recent outbreaks have predominantly involved young adults, nearly all of whom had a history of vaccination during childhood, most with the recommended 2-dose schedule. Evidence of waning immunity has led to suggestions that vaccination with a third dose during adolescence might be an effective measure to prevent outbreaks.1 However, outbreaks in Australia and overseas have subsided without this being routinely implemented as yet.
Routine meningococcal C vaccination for infants and the high-school catch-up program, implemented from 2003, have resulted in a significant decrease in cases associated with serogroup C. However, the predominant serogroup responsible for disease remains serogroup B and vaccines in development are keenly awaited.131
Pandemic and seasonal influenza and pneumonia are other diseases with higher rates in Aboriginal and Torres Strait Islander people than in other people. This has been attributed to higher susceptibility to influenza disease and the prevalence of comorbidities. For Aboriginal and Torres Strait Islander people aged ≥50 years there is evidence of a decline in influenza hospitalisations from 1999, suggesting some possible impact of the National Indigenous Pneumococcal and Influenza Immunisation (NIPII) Program. Since 2010, seasonal influenza vaccine has been funded for all Aboriginal and Torres Strait Islander people aged ≥15 years. This broadening of the vaccination program has the potential to result in a further reduction in the disease burden of seasonal influenza in this population. However, infrequent but low coverage estimates in the 50–64 years age group and the lack of coverage data in the 15–49 years age group, highlight the need for improved coverage data to facilitate program implementation.
For invasive pneumococcal disease, a substantial overall reduction in notifications of IPD caused by serotypes contained in the 7vPCV has been seen among Aboriginal and Torres Strait Islander children after the introduction of vaccination. However, due to a lower proportion of IPD being caused by 7vPCV types prior to vaccine introduction, delayed vaccination, and a higher prevalence of risk factors associated with IPD among Aboriginal and Torres Strait Islander people, the decline in IPD notifications has been less marked than in other people. The higher valency vaccines (10vPCV and 13vPCV) that replaced 7vPCV may result in a greater effect on both invasive and non-invasive disease. Recent evidence of an increase in IPD in Aboriginal and Torres Strait Islander people aged ≥50 years, together with infrequent, unvalidated and low coverage estimates, highlight the need for improved coverage data.
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