Rotavirus is a common cause of gastrointestinal infection in young children; almost all children will acquire infection and antibodies by the age of 3 years.3 The severity of rotavirus infection is age dependent. Infections are more likely to be severe in children 3–24 months of age. Rotavirus infection can range from asymptomatic infection to mild diarrhoea to severe gastroenteritis with dehydration. Most disease is mild but about 1 in 75 children will develop severe disease causing dehydration.3

Relevant vaccine history

2006

  • Vaccination recommended and funded for infants in the Northern Territory using monovalent rotavirus vaccine in a 2-dose schedule (2 and 4 months of age).

2007

  • Funded national immunisation commenced, with each state and territory using either a 2-dose schedule of monovalent rotavirus vaccine (2 and 4 months of age) or a 3-dose schedule of pentavalent rotavirus vaccine (2, 4 and 6 months of age).

Key points

Overall, there has been a substantial decline in hospitalisations from rotavirus since the introduction of the Australian rotavirus immunisation program. The decline in Aboriginal and Torres Strait Islander people has been less than that in other people. Low vaccination coverage due to delayed vaccination and upper age limits for rotavirus vaccination, and low vaccine effectiveness for some circulating genotypes may be contributing factors.

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Disease trends

Rotavirus was made notifiable in different jurisdictions at varying times during this reporting period; hence rotavirus notification data are not included in this report. There has been an overall downward trend in rotavirus hospitalisations in children <1 year of age since 2001/2002 (Figure 2.10.1). Vaccination was introduced in the Northern Territory in 2006 and in other states in 2007. Since then, the rates have declined significantly in Aboriginal and Torres Strait Islander infants aged <1 year, while the rates in the 1–4 years age group have remained stable.

Figure 2.10.1: Rotavirus hospitalisation rates and 95% confidence intervals, selected Australian states,* 1999 to 2010, by age group (<5 years) and Indigenous status

Figure 2.10.1: is a line chart showing Rotavirus hospitalisation rates and 95% confidence intervals, selected Australian states, 1999 to 2010. A link to a text description follows.

* Jurisdictions with satisfactory data quality over the whole time period; see Appendix A (Northern Territory, Queensland, South Australia, Western Australia).

† Hospitalisations where the date of separation was between 1 July 1999 and 30 June 2010.

Text description of Figure 2.10.1 (TXT 1 KB)

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Age-specific hospitalisation rates are presented for Aboriginal and Torres Strait Islander and other people, comparing the periods before and after vaccine introduction in 2006/2007. In the period 2002/2003–2009/2010, excluding the vaccine introduction year 2006/2007, there were a total of 8,093 rotavirus hospitalisations in the Northern Territory, Queensland, South Australia and Western Australia. Of those, 2,380 (29%) were aged <1 year, 4,772 (59%) 1–4 years and 941 (12%) ≥5 years. Of the total 8,093 hospitalisations, 1,159 (14%) were reported in Aboriginal and Torres Strait Islander people. There was an overall decline in hospitalisation rates in Aboriginal and Torres Strait Islander children aged <5 years after vaccine introduction, though declines were less than those in other children (Table 2.10.1). There was a 38% reduction in the hospitalisation rate in Aboriginal and Torres Strait Islander children <1 year of age, compared to a 71% reduction in other infants in that age group. There was a small increase in hospitalisation rates in Aboriginal and Torres Strait Islander people, but not in others ≥5 years of age.

Table 2.10.1: Rotavirus hospitalisation rates, comparing pre-vaccine period 2002 to 2006 and post-vaccine period 2008 to 2010, selected Australian states,* by age group and Indigenous status
Age group (years) Pre-vaccine rates
2002/2003–2005/2006
Post-vaccine rates
2008/2009–2009/2010
Indigenous Other Rate ratio Indigenous Other Rate ratio

* Northern Territory, Queensland, South Australia, Western Australia.

† Average annual age-specific rate per 100,000 population, periods are financial years (July to June).

§ Indicates statistically significant, 95% confidence intervals do not overlap 1.0.

<1
2,273.4
344.8
6.6§
1,404.1
99.4
14.1§
1–4
351.7
246.0
1.4§
327.3
70.0
4.7§
>5
1.5
2.3
0.7
2.6
1.9
1.4

There were 1–4 deaths reported from the five jurisdictions (New South Wales, the Northern Territory, Queensland, South Australia and Western Australia) for the period 2006–2010 with rotavirus as the underlying cause (the ABS provides ranges when absolute numbers of deaths are low). None of these deaths were reported in Aboriginal and Torres Strait Islander people. There were 5–8 deaths recorded with rotavirus as either the underlying or a contributing cause, of which 1–4 were reported in Aboriginal and Torres Strait Islander people.

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Comment

In the pre-vaccine period, there was a higher burden of rotavirus in Aboriginal and Torres Strait Islander children than in other children, especially in those <2 years of age. Aboriginal and Torres Strait Islander children were at higher risk of being notified with or hospitalised due to rotavirus, and when hospitalisation occurred it was at an earlier age and for longer than other children.95,96

Since vaccine introduction in Australia, there have been reductions in rotavirus disease notifications97 and hospitalisations98-100 in children in the target age group and herd immunity effects in other age groups.98,100 The reductions in rotavirus-coded hospitalisations reported here in children aged <5 years are an underestimate of the total impact of vaccination; in another study, the reduction in other acute gastroenteritis hospitalisations not coded as due to rotavirus was 6.5 times greater than in those coded as rotavirus.100 Although there has been a substantial post-vaccine decline in rotavirus hospitalisations in Aboriginal and Torres Strait Islander children, it has been less marked than declines in other children. This is in contrast to the United States where, although there was a greater burden of disease in American Indian and Alaskan Native children than in other children before the introduction of vaccination, the reductions after vaccine introduction have been similar in both groups.101 Analysis by further age breakdowns in ages ≥5 years has not been presented in this report. However, a modest increase has been reported in national hospitalisation rates in those aged ≥65 years.100 This may be related to increased testing for rotavirus and other agents of gastroenteritis, such as adenovirus and norovirus, in the elderly.99

There are two rotavirus vaccines available; both are oral live attenuated vaccines. Rotarix® is a monovalent human G1P(8) vaccine that requires 2 doses (2 and 4 months of age), and RotaTeq® is a pentavalent human–bovine reassortant vaccine containing G1, G2, G3, G4 and P(8) genotypes, which requires 3 doses (2, 4 and 6 months of age). Immunity from the monovalent vaccine may cover a narrower range of genotypes.3 Monovalent vaccine effectiveness was found to be 78% in Northern Territory Aboriginal and Torres Strait Islander children during an outbreak of G9P(8) rotavirus in 2007,102 but only 19% during an outbreak of G2P(4) in 2009.103 Lower effectiveness of oral vaccines has been shown in developing country settings, possibly related to competition from other gastrointestinal pathogens, poorer immune health, higher maternal antibody levels and/or interference from breast milk,3 and it is conceivable that these factors may also have an impact in some Aboriginal and Torres Strait Islander communities.

However, while the two vaccines may or may not differ in their effectiveness against particular genotypes, the vaccination coverage achieved from the 2-dose schedule of monovalent vaccine is higher than for the 3-dose pentavalent vaccine. Coverage for Aboriginal and Torres Strait Islander infants at 12 months of age is only 66% for the 3-dose schedule and 77% for the 2-dose schedule. Rotavirus vaccine coverage is much lower (17%) in Aboriginal and Torres Strait Islander children than in other children for the 3-dose schedule, which is a greater disparity than for the 2-dose rotavirus (9%) or non-rotavirus vaccines (7%). This is probably related to the strict upper age cut-offs for rotavirus vaccines and more frequent delayed vaccination of Aboriginal and Torres Strait Islander infants (see ‘Vaccination coverage’ chapter).

This again underlines the importance of improving timely delivery of immunisation to Aboriginal and Torres Strait Islander children. It also shows the impact of upper age cut-offs for rotavirus vaccines, especially for Aboriginal and Torres Strait Islander children, and an assessment of their costs and benefits may be warranted. Close monitoring of the circulating genotypes of rotavirus and their relationship to vaccine use is also important.