Cost effectiveness and delivery study for future HIV vaccines

Managing health care decisions and improvement through simulation modeling

Simulation modeling is a way to test changes in a computerized environment to give ideas for improvements before implementation. This article reviews research literature on simulation modeling as support for health care decision making. The aim is to investigate the experience and potential value of such decision support and quality of articles retrieved. A literature search was conducted, and the selection criteria yielded 59 articles derived from diverse applications and methods. Most met the stated research-quality criteria. This review identified how simulation can facilitate decision making and that it may induce learning. Furthermore, simulation offers immediate feedback about proposed changes, allows analysis of scenarios, and promotes communication on building a shared system view and understanding of how a complex system works. However, only 14 of the 59 articles reported on implementation experiences, including how decision making was supported. On the basis of these articles, we proposed steps essential for the success of simulation projects, not just in the computer, but also in clinical reality. We also presented a novel concept combining simulation modeling with the established plan-do-study-act cycle for improvement. Future scientific inquiries concerning implementation, impact, and the value for health care management are needed to realize the full potential of simulation modeling.

Modeling HIV vaccines in Brazil: assessing the impact of a future HIV vaccine on reducing new infections, mortality and number of people receiving ARV

Background

The AIDS epidemic in Brazil remains concentrated in populations with high vulnerability to HIV infection, and the development of an HIV vaccine could make an important contribution to prevention. This study modeled the HIV epidemic and estimated the potential impact of an HIV vaccine on the number of new infections, deaths due to AIDS and the number of people receiving ARV treatment, under various scenarios.

Methods and Findings

The historical HIV prevalence was modeled using Spectrum and projections were made from 2010 to 2050 to study the impact of an HIV vaccine with 40% to 70% efficacy, and 80% coverage of adult population, specific groups such as MSM, IDU, commercial sex workers and their partners, and 15 year olds. The possibility of disinhibition after vaccination, neglecting medium- and high-risk groups, and a disease-modifying vaccine were also considered. The number of new infections and deaths were reduced by 73% and 30%, respectively, by 2050, when 80% of adult population aged 15–49 was vaccinated with a 40% efficacy vaccine. Vaccinating medium- and high-risk groups reduced new infections by 52% and deaths by 21%. A vaccine with 70% efficacy produced a great decline in new infections and deaths. Neglecting medium- and high-risk population groups as well as disinhibition of vaccinated population reduced the impact or even increased the number of new infections. Disease-modifying vaccine also contributed to reducing AIDS deaths, the need for ART and new HIV infections.

Conclusions

Even in a country with a concentrated epidemic and high levels of ARV coverage, such as Brazil, moderate efficacy vaccines as part of a comprehensive package of treatment and prevention could have a major impact on preventing new HIV infections and AIDS deaths, as well as reducing the number of people on ARV. Targeted vaccination strategies may be highly effective and cost-beneficial.

Potential population health outcomes and expenditures of HIV vaccination strategies in the United States

Estimating the potential health benefits and expenditures of a partially effective HIV vaccine is an important consideration in the debate about whether HIV vaccine research should continue. We developed an epidemic model to estimate HIV prevalence, new infections, and the cost-effectiveness of vaccination strategies in the U.S. Vaccines with modest efficacy could prevent 300,000-700,000 HIV infections and save $30 billion in healthcare expenditures over 20 years. Targeted vaccination of high-risk individuals is economically efficient, but difficulty in reaching these groups may mitigate these benefits. Universal vaccination is cost-effective for vaccines with 50% efficacy and price similar to other infectious disease vaccines.

Demand forecasting for preventive AIDS vaccines: economic and policy dimensions

BACKGROUND

An AIDS vaccine could play a very significant role in reversing the HIV pandemic, saving millions of lives. For a vaccine to have such an impact, it must be widely available and adopted and taken up rapidly in the countries most affected. A demand-forecasting model provides a valuable tool that can guide R&D spending decisions and identify policy actions to help achieve these goals.

OBJECTIVE

To identify the key determinants of vaccine demand, model global adoption and uptake dynamics, estimate potential demand and revenues associated with future preventive AIDS vaccines, and to conduct sensitivity analyses to assess the impact of each parameter on demand.

METHODS

A discrete, deterministic, linear, predictive mathematical model based on stratified population averages with a 30-year time horizon was developed to assess scenarios of future demand. This forecasting model was used to explore the effects of vaccine characteristics and a variety of regulatory, political, financial and health service factors on future demand and revenues. The intervention modelled was a preventive AIDS vaccine (efficacy: 30-90%; duration of protection: 3-5 years; in a two-dose prime-boost combination). The main outcome measure was the number of complete courses of vaccine administered.

RESULTS

The model suggests that demand for a preventive AIDS vaccine with a medium efficacy (50%) and duration of protection (3 years) would average 68 million courses annually over a 30-year period. Under different scenarios, demand would peak at 38-152 million courses annually. On the basis of tiered pricing across public and private markets ($US2-100 per dose), these levels of peak demand would translate into $US2.5-5.5 billion in peak annual sales revenues. Private markets and high-income countries account for small volumes but large shares of projected revenues, while low-income countries account for large volumes and more modest, but still significant, sales revenues. Vaccinations to 'catch-up' those who are missed or not eligible for routine annual programmes (whether adolescent or high-risk populations) would account for 20-35% of cumulative vaccination courses across all scenarios. Demand was found to be sensitive to vaccine efficacy, duration of protection and price. Efforts to expedite regulatory review processes, improve immunization infrastructure and reduce political constraints could increase demand for an AIDS vaccine by 40 million additional courses a year compared with the medium efficacy (baseline) vaccine forecast.

CONCLUSIONS

Our model can provide vaccine developers with credible estimates of market potential for an AIDS vaccine, and with a tool that can be used to improve forecasts over time as AIDS vaccine science progresses. It can also help governments to identify and pursue those policies that could best strengthen demand and uptake of a safe and effective preventive AIDS vaccine.

HIV/AIDS vaccination in adolescents would be efficient and practical when vaccine supplies are limited

The first HIV/AIDS vaccines are likely to be expensive and limited in supply, and developing countries with generalized HIV/AIDS epidemics will need to distribute the limited vaccine stock in a manner that is both efficient and practical. This analysis compares seven strategies for distributing an HIV/AIDS vaccine in different South African sub-populations, using a mathematical model. If vaccination is not coupled with HIV screening, vaccination of 16-year olds in school is likely to be the most efficient strategy for averting HIV infections in the short term. If coupled with screening, vaccination of sex workers and patients seeking STD treatment would be more efficient, but these gains in efficiency would have to be weighed against the practical challenges associated with vaccinating 'high risk' groups and conducting screening.

Use of tenofovir disoproxil fumarate and emtricitabine combination in HIV-infected patients

With the continuing spread of HIV infection, particularly in developing countries, cost-effective treatment for its management is a high priority. Truvada (Gilead Sciences) is a single combination pill of the nucleotide reverse transcriptase inhibitors tenofovir disoproxil fumarate and emtricitabine, which is used once daily. It is anticipated to be a clinically potent combination that is free of short-term irritating toxicity. The drug has recently been licensed but there are currently little clinical efficacy data regarding its use. The limited published data have indicated that emtricitabine and lamivudine have equivalent potency, and randomised controlled trials have produced evidence of the efficacy of lamivudine combined with tenofovir disoproxil fumarate in a regimen containing either the non-nucleoside reverse transcriptase inhibitor efavirenz or a protease inhibitor lopinavir/ritonavir. In these trials, long-term durability data are available for < or = 96 weeks.

Assistência aos pacientes com HIV/Aids no Brasil

O trabalho teve por objetivo avaliar a assistência à população com Aids no Brasil e a capacidade do Sistema Único de Saúde (SUS) de prover intervenções para enfrentamento da epidemia e discutir a sustentabilidade da iniciativa brasileira de distribuição universal e gratuita dos anti-retrovirais. O trabalho considerou dados originais de uma pesquisa sobre a capacidade potencial de distribuição de uma futura vacina anti-HIV no Brasil, envolvendo 119 entrevistados. Nas abordagens da assistência hospitalar e da assistência farmacêutica foram utilizados dados do Sistema de Informações Hospitalares do SUS e do Sistema de Controle Logístico de Medicamentos do Programa Nacional de DST/Aids. Os resultados mostraram bom desempenho da política de distribuição de anti-retrovirais. Entretanto, o acesso ao tratamento de doenças oportunistas foi deficitário. Os valores pagos pelo Sistema Único de Saúde pelas internações por Aids mantiveram-se muito baixos, com valor médio em torno de R$700,00, em 2004. A assistência a pacientes com HIV/Aids no Brasil tem sido tratada como um direito do cidadão, com o respaldo de uma articulação efetiva entre as esferas de governo e a sociedade civil. Os desafios que se colocam atualmente dizem respeito ao monitoramento mais fino dos processos e resultados obtidos e à sustentabilidade da distribuição universal e gratuita de anti-retrovirais.