Return on investment in needle and syringe programs in Australia: report

3.4 Number of HIV infections prevented through the introduction of NSPs

Page last updated: 2002

3.4.1 Estimates of injecting drug users living with HIV/AIDS with NSP introduction

Estimates and projections of the number of people living with HIV acquired through injecting drug use by disease stage and HIV/AIDS-related deaths from 1981 though 2070 are provided in Table 3.4.1 (in Appendix C). The number of people living with HIV/AIDS is estimated to have peaked in the early 1990s at approximately 470 cases, with a peak in people living with AIDS of less than 100 in the late 1990s. The cumulative number of deaths from HIV/AIDS by 2010 is projected to be approximately 350.

3.4.2 Estimates of injecting drug users living with HIV/AIDS without NSP introduction

Corresponding estimates and projections of the number of people living with HIV/AIDS by disease stage and HIV/AIDS-related deaths without the introduction of NSPs are provided in Table 3.4.2 (in Appendix C). The number of people living with HIV/AIDS was estimated to peak in 2000 at approximately 26,000, with a peak in people living with AIDS of almost 3,000 in 2010. The estimated cumulative number of deaths from HIV/AIDS by 2010 was approximately 5,000.

3.4.3 Estimates of HIV infections and HIV/AIDS deaths prevented through NSP introduction

Estimates of the number of HIV infections and HIV/AIDS deaths prevented through the introduction of NSPs (over the period 1988 through 2000) are provided in Table 3.4.3 (in Appendix C). By the year 2000, approximately 25,000 HIV infections are estimated to have been prevented since the introduction of NSP in 1988, and by 2010 approximately 4,500 deaths are projected to have been prevented.

3.4.4 Estimates of HIV/AIDS cases prevented by disease stage and diagnosis category

An estimated 90% of the Australian HIV-infected population is diagnosed (NCHECR 2001). We have assumed that the proportion diagnosed is 100% for people with AIDS, and would be higher among people with progressive HIV disease (CD4<500/mm3) than people with early HIV disease (CD4 >500/mm3) (Table 3.4.4).

Based on data from the Australian HIV Observational Database (AHOD) over the period January 1997- March 2001, 71% of people with diagnosed HIV infection in Australia were receiving antiretroviral therapy. The proportion of injecting drug users receiving antiretroviral therapy was not significantly different to other risk categories (63% versus 71%, p>0.05). The proportion of people receiving antiretroviral therapy is 90% for AIDS, 50% for CD4 < 500/mm3, and 69% for CD4 > 500/mm3. Due to probable selection bias in AHOD for people with early HIV disease who are receiving antiretroviral therapy, the population level proportion is likely to be somewhat lower. Therefore, 40% of people with early stage HIV disease have been estimated to be receiving antiretroviral therapy.

Estimates of the number of HIV/AIDS cases prevented through the introduction of NSP by disease category and diagnosis category are provided in Table 3.4.5 (in Appendix C). These estimates form the basis for the calculation of the health care cost savings provided by the introduction of NSPs.
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Table 3.4.4 Proportions of people with diagnosed HIV and antiretroviral therapy use by disease stage

Disease stageDiagnosed/Undiagnosed (%)Antiretroviral therapy among diagnosed group1
Early HIV disease (CD4 >= 500/mm3)
80/20
40%
Progressive HIV disease (CD4 < 500/mm3)
90/10
70%
AIDS
100/0
90%

1 All people with undiagnosed HIV are assumed to not be receiving antiretroviral therapy.