Epidemiologic modeling to evaluate prevention of mother-infant HIV transmission in Ontario.

Abstract

To evaluate the impact of the Ontario HIV screening program to reduce mother-infant HIV transmission, this study estimated the proportion of preventable transmissions that were prevented. Using an iterative spreadsheet model, incidences of HIV infection, AIDS, and AIDS mortality in Ontario women were estimated by exposure category. The number of HIV-infected infants born to HIV-infected mothers was then estimated from conception and abortion rates of HIV-infected women of childbearing age and surveillance data. Finally, the proportion of HIV-infected mothers who received antiretroviral prophylaxis (ARP) was assessed. HIV prevalence in 2001 among women of childbearing age was 1.05 per 1000. From 1984-2001, 764 infants were born to HIV-infected mothers and 180 were infected. From mid-1994-2001, 214 (39%) of the estimated 544 HIV-infected mothers were diagnosed; almost all received ARP. Of 118 preventable infections among infants born in this period, 39 (33%) were prevented. In 2001, only 46% of preventable infections were prevented and 11 preventable transmissions occurred. HIV prevalence among women in Ontario increased >4-fold from 1990 to 2001. Fewer than half of HIV-infected mothers received ARP and preventable HIV infections continue to occur. Measures to further increase uptake of prenatal HIV screening must be instituted.