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Monday, 18 October 2004 - 11:45 AM

This presentation is part of: Oral Concurrrent Session A - Public Health 1

COST EFFECTIVENESS OF PARTIALLY EFFECTIVE HIV VACCINES IN THE ERA OF HIGHLY ACTIVE ANTIRETROVIRAL THERAPY

Douglas K. Owens, MD, MS1, John F. Cavallaro, MA2, Donna Edwards, PhD3, and Ross Shachter, PhD2. (1) Stanford University, Center for Health Policy / Center for Primary Care and Outcomes Research, Stanford, CA, (2) Stanford University, Management Science and Engineering, Stanford, CA, (3) Sandia National Laboratories, Modeling, Livermore, CA

A vaccine remains the best hope for prevention of HIV worldwide. Difficulties in vaccine development have led many authorities to conclude that vaccines are likely to be only partially effective. We analyzed the costs and benefits of partially effective HIV vaccines in a population of men who have sex with men (MSM) in the era of highly active antiretroviral therapy (HAART).

We developed a dynamic transmission model to evaluate the total costs and benefits of preventive and therapeutic vaccines in a population of MSM in San Francisco, California (MSM population size 46,800), from the societal perspective. We used published and unpublished data on prevalence, incidence, and sexual risk behavior from San Francisco. We report findings for an early-stage epidemic in which prevalence was 10% and increasing. We used data on infectivity during the course of HIV disease, along with behavioral data to estimate transmission. We assumed that patients with symptomatic disease or AIDS would receive HAART. We used published data on costs of therapy, and evaluated vaccines of various duration and efficacy. Our base case preventive vaccine had 75% efficacy and lasted 10 years; the base case therapeutic vaccine added 5 years to length of life. We assumed a vaccine cost of $1000.

Over 20 years, the base-case preventive vaccine averted 5917 infections, added 6299 quality-adjusted life years (QALYs), and saved $123 million. As long as vaccine efficacy was greater than 10%, the vaccine cost less than $50,000 per QALY gained. Vaccines that had greater than 25% efficacy were cost saving. The effect of a therapeutic vaccine on the number of infections depends on the reduction in infectivity. A therapeutic vaccine that reduced infectivity by 50% averted 1,089 infections; if infectivity was reduced by 90%, almost twice as many infections were averted (1,965). Therapeutic vaccines were cost saving as long as they added at least 1 year to length of life, and risk behavior did not increase.

HIV vaccines of very modest efficacy provide enormous health benefit and are economically efficient. Vaccines with more than modest efficacy are cost saving over a wide variety of assumptions, even in the era of HAART. These findings imply that it is reasonable to initiate phase III efficacy trials for vaccines with modest expected efficacy.


See more of Oral Concurrrent Session A - Public Health 1
See more of The 26th Annual Meeting of the Society for Medical Decision Making (October 17-20, 2004)