Modeling the Population Level Effects of an HIV-1 Vaccine in an Era of Highly Active Antiretroviral Therapy
First generation HIV vaccines may have limited ability to prevent infection. Instead, they may delay the onset of AIDS or reduce the infectiousness of vaccinated individuals who become infected. To assess the population level effects of such a vaccine, we formulate a deterministic model for the spread of HIV in a homosexual population in which the use of highly active antiretroviral therapy (HAART) to treat HIV infection is incorporated. The basic reproduction number R 0 is obtained under this model. We then expand the model to include the potential effects of a prophylactic HIV vaccine. The reproduction number R f is derived for a population in which a fraction f of susceptible individuals is vaccinated and continues to benefit from vaccination. We define f * as the minimum vaccination fraction for which R f ≤ 1 and describe situations in which it equals the critical vaccination fraction necessary to eliminate disease. When R 0 is large or an HIV vaccine is only partially effective, the critical vaccination fraction may exceed one. HIV vaccination, however, may still reduce the prevalence of disease if the reduction in infectiousness is at least as great as the reduction in the rate of disease progression. In particular, a vaccine that reduces infectiousness during acute infection may have an important public health impact especially if coupled with counseling to reduce risky behavior.
KeywordsAIDS Basic reproduction number Epidemic models HAART HIV Vaccines
- Bartlett, J., Lane, H., Anderson, J., Baker, A., Bozzette, S., Carpenter, C., Delaney, M., El-Sadr, L., Fletcher, C. et al., 2006. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. DHHS-Office of AIDS Research Advisory Council. Google Scholar
- Burr, C., 1998. Of AIDS and altruism. US News World Rep. 124(13), 60–1. Google Scholar
- Gray, R., Wawer, M., Brookmeyer, R., Sewankambo, N., Serwadda, D., Wabwire-Mangen, F., Lutalo, T., Li, X., vanCott, T., Quinn, T., 2001. Probability of HIV-1 transmission per coital act in monogamous, heterosexual, HIV-1-discordant couples in Rakai, Uganda. Lancet 357(9263), 1149–153. CrossRefGoogle Scholar
- Hoyert, D., Kung, H., Smith, B., 2005. Deaths: preliminary data for 2003. Nat. Vital Stat. Rep. 53(15), 1–8. Google Scholar
- IAVI, 2007. International AIDS Vaccine Initiative vaccine database. http://www.iavi.org.
- Lyles, R., Munoz, A., Yamashita, T., Bazmi, H., Detels, R., Rinaldo, C., Margolick, J., Phair, J., Mellors, J., 2000. Natural history of human immunodeficiency virus type 1 viremia after seroconversion and proximal to AIDS in a large cohort of homosexual men. J. Infect. Dis. 181(3), 872–80. CrossRefGoogle Scholar
- Macey, R., Oster, G., 2000. Berkeley madonna. Version 801. Google Scholar
- Pitisuttithum, P., Gilbert, P., Gurwith, M., Heyward, W., Martin, M., van Griensven, F., Hu, D., Tappero, J., Choopanya, K. , 2006. Randomized, double-blind, placebo-controlled efficacy trial of a bivalent recombinant glycoprotein 120 HIV-1 vaccine among injection drug users in Bangkok, Thailand. J. Infect. Dis. 194(12), 1661–671. CrossRefGoogle Scholar
- Sifakis, F., Flynn, C., Metsch, L., LaLota, M., Murrill, C., Koblin, B., Bingham, T., McFarland, W., Raymond, H., Behel, S. , 2005. HIV prevalence, unrecognized infection, and HIV testing among men who have sex with men-five US cities, June 2004–April 2005. Morb. Mortal. Wkly. Rep. 54(24), 597–01. Google Scholar
- Thiebaut, R., Jacqmin-Gadda, H., Babiker, A., Commenges, D., the Cascade Collaboration, 2005. Joint modelling of bivariate longitudinal data with informative dropout and left censoring, with application to the evolution of CD4+ cell counts and HIV RNA viral load in response to treatment of HIV infection. Stat. Med. 24, 65–2. CrossRefMathSciNetGoogle Scholar
- UNAIDS, 2007.2007 AIDS epidemic update. http://www.unaids.org/en/HIV_data/2007EpiUpdate/default.asp.
- Vittinghoff, E., Douglas, J., Judson, F., McKirnan, D., MacQueen, K., Buchbinder, S., 1999. Per-contact risk of human immunodeficiency virus transmission between male sexual partners. Am. J. Epidemiol. 150(3), 306–11. Google Scholar