Objective: To estimate the reduction in AIDS incidence, if any, which has occurred in Australia following the availability of new combination antiretroviral treatments from 1995.
Design: Analyses were based on national surveillance data.
Methods: Back-projection analyses based on quarterly AIDS counts to the end of 1994 were used to estimate the numbers of AIDS diagnoses which would have occurred if new treatments had not reduced the rate of progression to AIDS. Estimates of the reduction in AIDS diagnoses between 1995 and 1998 were made by subtracting the observed delay-adjusted AIDS counts from the predicted AIDS incidence.
Results: AIDS incidence between 1995 and 1998 was estimated to have been reduced by 1093 cases (33%) following the availability of new antiretroviral treatments (95% confidence interval 831 (25%) to 1425 (43%) cases). The majority of this reduction in AIDS incidence was estimated to have occurred during 1997 (434 cases) and 1998 (427 cases).
Conclusions: AIDS incidence in Australia has declined since 1995 coincidental with introduction of new antiretroviral treatments. In particular, the more rapid decline in AIDS incidence since mid-1996 coincided with the availability and widespread uptake of combinations including protease inhibitors.