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Browse POLICY Project (1995-2006) Materials

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  • Many people see an effective AIDS vaccine as the best solution to the HIV/AIDS pandemic. A considerable amount of funding and research effort is devoted to developing an effective vaccine. Ten years ago many scientists had hoped that a vaccine would be available by now. Most scientists are still optimistic that vaccines will be developed and many candidates are being tested. Programs to implement vaccination need to be developed in order to be ready when vaccines do become available. The nature of those programs will depend on the characteristics of each vaccine. How much does it cost? How effective is it? How long does protection last? The answers to these and other questions will help determine issues such as: Who should be vaccinated? Should regular re-vaccinations be scheduled? How much funding will be needed? Do vaccination campaigns need to be supported with safe sex messages? What will be the impact of the vaccine on the epidemic? This study uses two computer simulation models to investigate the effects of various vaccine characteristics and implementation strategies on the impact and costeffectiveness of vaccines in different contexts. A simulation model from the Imperial College is applied to data from rural Zimbabwe and the iwgAIDS model is applied to Kampala and Thailand. The models are used to investigate the effects of efficacy, duration, cost and type of protection on impact and cost-effectiveness. The models also illustrate the merits of targeting public subsidies to various population groups: all adults, teenagers, high- risk groups and reproductive age women. The impact of vaccines on the epidemic is compared with the impact of other prevention interventions, such as condom use and behavior change. Finally, the models are used to explore the extent to which behavioral reversals may erode the positive benefits of the vaccine. A highly effective, long- lasting, inexpensive vaccine would be ideal and could make a major contribution to controlling the HIV/AIDS pandemic. However, vaccines that do not attain this ideal can still be useful. A vaccine with 50 percent efficacy and 10 years duration supplied to 65 percent of all adults could reduce HIV incidence by 25 to 60 percent depending on the context and stage of the epidemic. Better efficacy and longer duration would provide even more impact. Programs focused on teenagers or high-risk populations have less overall impact but would provide significant benefits at much less cost than those reaching all adults. Behavioral reversals could erode much of the benefits of vaccination programs so it will be important to combine vaccination with continued messages about the importance of safe behaviors. The cost of the vaccines is not known at this time. At a cost of $10 or $20 per person vaccinated the cost per infection averted would be as low or lower than other prevention interventions. Higher costs for the vaccines and the need for many booster shots could reduce the cost-effectiveness significantly.
    English
    Vaccine_World_Bank_article.pdf