Vaccine Preventable Diseases in Australia, 2005 to 2007

5.3 Diseases with vaccination programs targeted to specific population subgroups or settings

Page last updated: 24 December 2010

Influenza, Q fever, hepatitis A

Influenza

During this reporting period, annual seasonal influenza vaccination was recommended for all Australians aged ≥65 years, all Aboriginal and Torres Strait Islander people aged ≥15 years, and all individuals aged ≥6 months who were predisposed to severe influenza or its complications, with the intention of protecting those who were more vulnerable to severe outcomes from influenza during each season. Australians aged ≥65 years, and Aboriginal and Torres Strait Islander people who were aged ≥50 years or who had chronic medical conditions that predispose them to severe influenza, were eligible for annual vaccination under the NIP. The 2006–2007 period was notable for a substantially higher notification rate in 2007 than in any previous year since notifications became available in 2001. Hospitalisation data were not available for all of 2007 at the time of this analysis. With only one source of data it is difficult to determine the extent to which the increase reflects the relative severity of that influenza season. However, there are reasons to suspect that 2007 was a more severe influenza season than usual. The co-circulation of two common strains of virus, A/H3N2 and A/H1N1 (both antigenically different to the strains of the previous season), is unusual, as is an increase in reported deaths due to influenza, including seven in young children. However, an increase in testing for influenza after the reported child deaths is also expected to have contributed to the substantial increase in that year. The child deaths, three of which were in Western Australia, were followed by the decision to offer funded influenza vaccine to all children in Western Australia aged <5 years from the following influenza season. Influenza vaccine has been recommended and funded for US children aged 6–23 months since 2003,10,11 and, since 2006, for children up to the age of 5 years.12 In 2008, the US recommendation was further expanded to include all children aged 6 months to 18 years, to be commenced from the 2008/09 influenza season.13 Notwithstanding bias due to variable rates of documenting notifications or hospitalisations across different age groups, it is noteworthy that notification and hospitalisation rates in children <5 years of age in Australia were approximately 4 times greater than in the elderly aged ≥60 years.

Q fever

Australia is unique in having a Q fever vaccine available and used in a national program. The National Q Fever Management Program (NQFMP) was implemented in various jurisdictions at different times between 2001 and 2006. The program promoted and provided screening and vaccination services for those at highest risk of Q fever (meat and livestock industry workers and their families and those working on farms). By 2005, Q fever notification and hospitalisation rates declined to record low levels. There has been no further decline during the 2006–2007 period, with some evidence of a slight increase. Limited data on vaccination status of cases, as well as the absence of risk factor data on routine notifications, make it difficult to assess the relative importance of a range of non-program and program factors potentially affecting disease rates. Relevant non-program factors include variations in drought conditions, livestock slaughtering patterns, and the role of less high-risk exposure occupations and settings. With respect to program factors, the extent to which a pause in vaccine manufacture during the reporting period affected availability and use of Q fever vaccine and whether this contributed to the small changes in Q fever notifications and hospitalisations observed is unclear.

Hepatitis A

In Australia, as in other industrialised countries, hepatitis A occurs sporadically with periodic epidemic peaks related to point-source and community-wide outbreaks. Notification and hospitalisation rates continued to decline in the 2-year period examined in this report, a decline which has continued since the peaks in the late 1990s associated with a large foodborne outbreak and an epidemic in homosexual men and injecting drug users. Notification and hospitalisation rates are now at levels lower than any observed since the collection of current data sources began in the early 1990s. The epidemiology of hepatitis A differs significantly for the Indigenous population, where it has been endemic, compared with the non-Indigenous population. The greater disease burden in Indigenous children has been particularly pronounced in more remote areas. In 1999, an immunisation program commenced for Indigenous children aged 18 months to 6 years living in north Queensland. This was expanded in 2005 to include all Indigenous children aged 12–24 months in the Northern Territory, Queensland, South Australia and Western Australia. While this report is focused on patterns in the total population rather than Indigenous people in particular, a substantial impact from this program is expected, similar to that seen in north Queensland14 and targeted programs in the USA.15

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