The varicella-zoster virus (VZV) causes two distinct diseases, varicella (chickenpox) and herpes zoster (shingles) associated with reactivation of latent VZV. Varicella is highly contagious and generally a benign, self-limiting illness in children, but adults have a significantly higher case morbidity and mortality than children. Acute varicella may be complicated by secondary bacterial infection of the skin, pneumonia, encephalitis, cerebellar ataxia, arthritis, appendicitis, hepatitis, glomerulonephritis, pericarditis and orchitis.3 Herpes zoster is a reactivation of virus that has lain dormant, usually for years, following varicella infection. It consists of a painful, localised rash. The most common complication of herpes zoster is post-herpetic neuralgia; other potential complications include ophthalmic disease, neurological complications, secondary bacterial infections and scarring.3

Relevant vaccine history

2003

  • Varicella vaccine recommended for all children aged 18 months and 10–13 years without prior history of infection.

2005

  • Varicella vaccination funded nationally, at 18 months and 10–13 years of age, for children without prior history of infection.

2006

  • All jurisdictions commenced school-based catch-up varicella vaccination for one cohort each year of adolescents aged 10–13 years without prior history of infection.

Key points

In the post varicella vaccine period there has been a significant decline in the hospitalisation rate due to varicella (chickenpox) in both Aboriginal and Torres Strait Islander and other people.

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Disease trends

Over the period between 1999/2000 and 2009/2010 there has been an overall downwards trend in hospitalisations due to varicella infection in both Aboriginal and Torres Strait Islander and other people. Hospitalisation rates have been persistently higher in Aboriginal and Torres Strait Islander people, with the most recent peak in 2006/2007 followed by a decline to the lowest rates in 2008/2009 (Figure 2.11.1).

Figure 2.11.1: Varicella (chickenpox) hospitalisation rates and 95% confidence intervals, selected Australian states,* 1999 to 2010, by Indigenous status

Figure 2.11.1: is a line chart showing the Varicella (chickenpox) 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. Rates are age-standardised to the Australian Bureau of Statistics Australian population estimates for 2006.

Text description of Figure 2.11.1 (TXT 1 KB)

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In contrast, there has been an upward trend in hospitalisation rates for herpes zoster in Aboriginal and Torres Strait Islander people, after an initial drop in 2003/2004 (Figure 2.11.2). Zoster hospitalisation rates in other people have remained stable over the past 10 years.

Figure 2.11.2: Herpes zoster (shingles) hospitalisation rates and 95% confidence intervals, selected Australian states,* 1999 to 2010, by Indigenous status

Figure 2.11.2: is a line chart showing the Herpes zoster (shingles) hospitalisation rates and 95% confidence intervals, selected Australian states. 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. Rates are age-standardised to the Australian Bureau of Statistics Australian population estimates for 2006.

Text description of Figure 2.11.2 (TXT 1 KB)

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Hospitalisation data are presented for six jurisdictions (all except Tasmania and the Australian Capital Territory) by financial year for the period July 2005 to June 2010. Data for notifications are not presented due to the low level of completeness of the Indigenous status field in notification records.

A total of 5,162 hospitalisations for varicella were recorded during this reporting period, of which 279 (5.4 %) were reported in Aboriginal and Torres Strait Islander people. Hospitalisation rates were higher across all age groups in Aboriginal and Torres Strait Islander people (Table 2.11.1). The highest rate (39.9 per 100,000) was in the 0–4 years age group, with an Indigenous to non-Indigenous rate ratio of 2.0:1.

Table 2.11.1: Varicella (chickenpox) hospitalisations, selected Australian states, 2005 to 2010, by age group and Indigenous status
Age group
(years)
Indigenous status Hospitalisations* (2005–2010)
n Rate Rate ratio

* Hospitalisations (New South Wales, Northern Territory, Queensland, South Australia, Victoria, Western Australia only) where the date of separation was between 1 July 2005 and 30 June 2010.

† Average annual age-specific rate per 100,000 population.

‡ Includes cases with age unknown. Rates for all ages combined are age-standardised to the Australian Bureau of Statistics Australian population estimates for 2006.

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

0–4
Indigenous
125
39.9
2.0§
Other
1,225
19.9
5–14
Indigenous
67
10.8
1.7§
Other
798
6.3
15–24
Indigenous
25
5.0
1.5§
Other
448
3.3
25–49
Indigenous
46
5.8
1.4§
Other
1,452
4.1
>50
Indigenous
16
5.3
1.7§
Other
960
3.1
All ages
Indigenous
279
8.5
1.7§
Other
4,883
5.0

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A total of 25,607 hospitalisations for herpes zoster were recorded during this reporting period, of which 376 (1.5 %) were reported in Aboriginal and Torres Strait Islander people. Hospitalisation rates for herpes zoster increased with age, as expected (Table 2.11.2). Rates were higher in Aboriginal and Torres Strait Islander people than in other people across all age groups except those ≥50 years of age. The overall Indigenous to non-Indigenous rate ratio was 1.1:1 (not statistically significantly different to 1:1).

Table 2.11.2: Herpes zoster (shingles) hospitalisations, selected Australian states, 2005 to 2010, by age group and Indigenous status
Age group
(years)
Indigenous status Hospitalisations* (2005–2010)
n Rate Rate ratio

* Hospitalisations (New South Wales, Northern Territory, Queensland, South Australia, Victoria, Western Australia only) where the date of separation was between 1 July 2005 and 30 June 2010.

† Average annual age-specific rate per 100,000 population.

‡ Includes cases with age unknown. Rates for all ages combined are age-standardised to the Australian Bureau of Statistics Australian population estimates for 2006.

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

0–4
Indigenous
9
2.9
2.0§
Other
90
1.5
5–14
Indigenous
29
4.7
1.7§
Other
348
2.8
15–24
Indigenous
26
5.2
2.0§
Other
369
2.7
25–49
Indigenous
111
13.9
2.5§
Other
1,999
5.6
>50
Indigenous
201
67.0
0.9
Other
22,425
72.6
All ages
Indigenous
376
26.0
1.1
Other
25,231
23.8

There were 20 deaths reported from the five jurisdictions (New South Wales, the Northern Territory, Queensland, South Australia and Western Australia) for the period 2006–2010 with varicella (chickenpox) as the underlying cause and 37 deaths with varicella (chickenpox) as either the underlying or a contributing cause. There were no deaths reported in Aboriginal or Torres Strait Islander people with varicella as either the underlying or a contributing cause.

There were 75 deaths reported from the five jurisdictions (New South Wales, the Northern Territory, Queensland, South Australia and Western Australia) for the period 2006–2010 with herpes zoster as the underlying cause and 295 deaths with herpes zoster as either the underlying or a contributing cause. There were 1–4 deaths reported in Aboriginal and Torres Strait Islander people with herpes zoster as either the underlying or a contributing cause, all of which were in people aged ≥50 years (the ABS provides ranges when absolute numbers of deaths are low). Overall, 97% of deaths with herpes zoster as either the underlying or a contributing cause were recorded in people ≥50 years of age.

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Comment

In the post varicella vaccine period there has been a significant decline in varicella hospitalisation rates in both Aboriginal and Torres Strait Islander and other people, most markedly after national funding in 2005, but also from 2003 when there was significant use of the vaccine in the private market.104 The decreases have occurred only in the 0–4 years age group (data not shown). Although rates continue to be higher in Aboriginal and Torres Strait Islander people than in other people, varicella (chickenpox) has not been known to be of particular concern in Aboriginal and Torres Strait Islander communities.

The burden of hospitalisation due to zoster is actually larger than for varicella, as cases are more likely to require hospitalisation. However, there are no clear trends in zoster hospitalisation rates over the past decade. Universal varicella vaccination was hypothesised to contribute to zoster increases, due to reduced natural boosting.105 Apparent increases in zoster-related disease seen in Australia and elsewhere have been attributed to ageing populations and changes in drug use patterns and have also occurred in the absence of vaccine use.106

This analysis is limited by the absence of suitable data on the vast majority of varicella and zoster disease – cases which do not require hospitalisation. Data on notifications and emergency department admissions for varicella and zoster in Aboriginal and Torres Strait Islander people would provide valuable information on future emerging issues such as breakthrough disease and zoster incidence.