Predicting the impact of a partially effective HIV vaccine and subsequent risk behavior change on the heterosexual HIV epidemic in low- and middle-income countries: A South African example
Journal of Acquired Immune Deficiency Syndromes
Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT, United States; Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, United States; Center for Primary Care and Outcomes Research, Center for Health Policy, Stanford University, Stanford, CA, United States; Perinatal HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa; Department of Epidemiology and Public Health, Yale University, School of Medicine, 60 College Street, New Haven, CT 06510, United States
We developed a mathematical model to simulate the impact of various partially effective preventive HIV vaccination scenarios in a population at high risk for heterosexually transmitted HIV. We considered an adult population defined by gender (male/female), disease stage (HIV-negative, HIV-positive, AIDS, and death), and vaccination status (unvaccinated/vaccinated) in Soweto, South Africa. Input data included initial HIV prevalence of 20% (women) and 12% (men), vaccination coverage of 75%, and exclusive male negotiation of condom use. We explored how changes in vaccine efficacy and postvaccination condom use would affect HIV prevalence and total HIV infections prevented over a 10-year period. In the base-case scenario, a 40% effective HIV vaccine would avert 61,000 infections and reduce future HIV prevalence from 20% to 13%. A 25% increase (or decrease) in condom use among vaccinated individuals would instead avert 75,000 (or only 46,000) infections and reduce the HIV prevalence to 12% (or only 15%). Furthermore, certain combinations of increased risk behavior and vaccines with <43% efficacy could worsen the epidemic. Even modestly effective HIV vaccines can confer enormous benefits in terms of HIV infections averted and decreased HIV prevalence. However, programs to reduce risk behavior may be important components of successful vaccination campaigns. © 2007 Lippincott Williams & Wilkins, Inc.
Human immunodeficiency virus vaccine; acquired immune deficiency syndrome; adolescent; adult; article; behavior change; condom; death; drug efficacy; female; gender; heterosexuality; high risk population; human; Human immunodeficiency virus infection; income; major clinical study; male; mathematical model; prevalence; priority journal; risk; South Africa; vaccination; AIDS Vaccines; Computer Simulation; Condoms; Female; HIV Infections; Humans; Male; Models, Biological; Risk Factors; Sensitivity and Specificity; Sex Factors; Socioeconomic Factors; South Africa; Time Factors; Unsafe Sex