AEGiS-14IAC: The potential impact of Antiretroviral therapy and HIV vaccines on adult HIV incidence; model estimates for a rural population in Rakai District, Ugandan.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

The potential impact of Antiretroviral therapy and HIV vaccines on adult HIV incidence; model estimates for a rural population in Rakai District, Ugandan.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. LbOr02)

Gray R, Wawer M, Serwadda D, Sewankambo N, Li X, Mangen FW, Lutalo T, Quinn T, Gange SJ
Johns Hopkins University, Baltimore, United States

BACKGROUND: ART or HIV vaccines could reduce potentially control the epidemic. We modeled effects on transmission using data from Rakai, Uganda.

METHODS: A stochastic simulation model estimated HIV incidence, probabilities of transmission/ coital act and the reproductive number (Ro) with ART and HIV vaccines. Projection models estimated HIV prevalence to 2020.Empirical model inputs included HIV transmission probabilities/coital act by HIV viral load, age and gender, and sexual behaviors in a population with known distributions of HIV viral loads. Treatment scenarios used DHHS guidelines (viral loads 55,000 copies/mL) or earlier initiation, and varying levels of population coverage. The impact of therapy on viral load and continuity of treatment were derived from U.S. programs. Vaccine assumptions included preventive efficacies ranging from 25-75%.

RESULTS: Model estimated HIV incidence (1.57/100 py) approximated the observed incidence, and model estimated probability of transmission/act (0.0012) approximated observed probabilities. Using DHSS treatment guidelines, HIV incidence declines to 1.27/100 py, but Ro remained > 1.0, and the numbers of HIV+ persons increased over time. A preventive vaccine, with > 50% efficacy and > 50% population coverage could reduce Ro < 1.0. A preventive vaccine combined with ART, can decrease Ro <1.0 at moderate levels of population coverage. However, disinhibition, modeled as increased numbers of sex partners, in either the treated/vaccinated or total population, markedly diminishes intervention effectiveness.

CONCLUSION: ART alone cannot control the HIV epidemic and persons in need of therapy will increase over time. ART in combination with a low efficacy vaccine can control the epidemic. Behavioral disinhibition could offset these public health benefits.

Keywords: AEGIS, AIDS Vaccines, Incidence, HIV Infections, HIV Seropositivity, Viral Load, Prevalence, Rural Population, Sex Behavior, Disease Outbreaks, Antiretroviral Therapy, Highly Active, Sexual Partners, United States, Uganda, Adult, Human, therapy, epidemiology, drug therapy

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