In recent years much scientific literature has reported the repeated failures of potential HIV vaccines to pass the phase II and phase III trials. In 2008 a potential vaccine, developed by Merck, failed its phase III trial, for the second time. As a result, the NIAID (National Institutes of Allergy and Infectious Diseases), among others, began to debate and reconsider the cost and benefit of HIV vaccine research and development. In 2007-2008 Elisa Long, Margaret Brandeau, and Douglas Owens conducted a study assessing “the outcomes for a broad range of vaccine efficacy and costs, and the outcomes associated with either universal vaccination or vaccination targeted to high-risk groups.”
Demographic information of currently reported HIV-positive individuals in the U.S, including behavioral patterns, was extrapolated using a set of differential equations to establish a model simulating the HIV epidemic over a 20 year period. This model depicts the proposed transmission and progression of HIV/AIDS and the cost-effectiveness for various vaccine strategies. They took into account several variables, such as the thought that antiretroviral therapy would decrease an individual’s infectivity thus possibly reducing transmission probability; however, increased life-expectancy of individuals would also increase measure of sexual activity and/or needle-sharing behaviors thus potentially increasing transmission.
They estimated that without any vaccine program in place, 1.29 million new HIV cases would occur over a 20 year period. They projected that a universal vaccination program, with a 75% efficacy and lifetime duration, would prevent 912,000 cases (71%) over the 20 year period, with 196 million individuals being vaccinated. A vaccination program targeting uninfected high-risk groups could result in 774,000 cases (60%) being prevented, with 9 million individuals being vaccinated. Finally, the less efficient strategy, by targeting low-risk individuals, 187 million individuals would require vaccination in order to return a reduction by 110,000 cases (12%). The model also suggests that for only a 5 to 10-year protection period, still with 75% efficacy, and universal vaccinations, approximate 420,000 — 610,000 cases can be prevented. Vaccinating high-risk groups would, obviously, greatly reduce the prevalence of HIV among those individuals, but could also significantly decrease the prevalence among low-risk individuals, due to reduced secondary transmission. The analysis appeared to suggest that with a high-risk exclusive vaccination program, 75% efficacy and lifetime protection, the cost-savings in healthcare expenditures would approximate $31 billion.
Targeted vaccination of high-risk groups appears by far more efficient than universal vaccinations. However the authors suggest that should an effective vaccine be developed, a universal vaccine strategy should still be utilized in order to ensure most, if not all, high-risk individuals participate. As the authors only appear to take into account the cost analysis of the hypothetical 20 year period, they fail to address the costs, towards vaccine research, accrued over the previous 20+ years, as well as the costs to amount over the next indefinite number of years until full vaccine development. While I cannot speak to the cost-benefit versus sunken-costs of this research over the last 20 years, the increase in life expectancy of those HIV positive in the U.S., and the reduced transmission rate appear to be significant enough to continue research in vaccine developments.
Long, E.F., M.L Brandeau, D.K. Owens. 2009. Potential population health outcomes and expenditures of HIV vaccination strategies in the United States. Vaccine 27:5402—5410.
Really excellent writing and a nice summary of the paper. Who did you have in mind as your audience when writing this post? Did that influence how you wrote the post?
ReplyDeleteThanks for the comment :)
ReplyDeleteI sort of had lay-readers in mind when writing this post; which in turn provoked me to summarize the complicated methods as briefly as possible, and to refrain from utilizing any technical terminology.