Elsevier

Vaccine

Volume 29, Issue 36, 18 August 2011, Pages 6113-6124
Vaccine

The cost-effectiveness of a modestly effective HIV vaccine in the United States

https://doi.org/10.1016/j.vaccine.2011.04.013Get rights and content

Abstract

Background

The recent RV144 clinical trial showed that an ALVAC/AIDSVAX prime-boost HIV vaccine regimen may confer partial immunity in recipients and reduce transmission by 31%. Trial data suggest that efficacy may initially exceed 70% but decline over the following 3.5 years. Estimating the potential health benefits associated with a one-time vaccination campaign, as well as the projected benefits of repeat booster vaccination, may inform future HIV vaccine research and licensing decisions.

Methods

We developed a mathematical model to project the future course of the HIV epidemic in the United States under varying HIV vaccine scenarios. The model accounts for disease progression, infection transmission, antiretroviral therapy, and HIV-related morbidity and mortality. We projected HIV prevalence and incidence over time in multiple risk groups, and we estimated quality-adjusted life years (QALYs) and costs over a 10-year time horizon. We assumed an exponentially declining efficacy curve fit to trial data, and that subsequent vaccine boosters confer similar immunity. Variations in vaccine parameters were examined in sensitivity analysis.

Results

Under existing HIV prevention and treatment efforts, an estimated 590,000 HIV infections occur over 10 years. One-time vaccination achieving 60% coverage of adults could prevent 9.8% of projected new infections over 10 years (and prevent 34% of new infections in the first year) and cost approximately $91,000/QALY gained relative to the status quo, assuming $500 per vaccination series. Targeted vaccination strategies result in net cost savings for vaccines costing less than $750. One-time vaccination of 60% of all adults coupled with three-year boosters only for men who have sex with men and people who inject drugs could prevent 21% of infections for $81,000/QALY gained relative to vaccination of higher risk sub-populations only. A program attaining 90% vaccination coverage prevents 15% of new HIV cases over 10 years (and approximately 50% of infections in the first year).

Conclusions

A partially effective HIV vaccine with effectiveness similar to that observed in the RV144 trial would provide large health benefits in the United States and could meet conventionally accepted cost-effectiveness thresholds. Strategies that prioritize key populations are most efficient, but broader strategies provide greater total population health benefit.

Introduction

Despite dramatic increases in the availability of antiretroviral therapy for HIV in resource-limited settings, approximately two new infections occur worldwide for every person placed on treatment [1]. This observation highlights the urgent need for expanded HIV prevention efforts, including use of an HIV vaccine. After many years of disappointing results, several promising developments have provided more cause for optimism [2]. In 2009, a large phase III trial of an ALVAC and AIDSVAX vaccine (RV144) demonstrated modest protection from infection with HIV, with a 31% reduction among trial volunteers [3]. More recently, investigators have reported the development of broadly neutralizing antibodies, which provides potential new targets for vaccine development [4], [5].

The modest success of the RV144 trial prompted renewed interest in understanding whether the use of a partially effective HIV vaccine would improve health outcomes sufficiently to justify its use [6], [7], [8], [9], [10], [11]. In particular, although the RV144 trial showed an overall effectiveness of 31%, vaccine efficacy was likely higher (approximately 70%) in the first year and rapidly declined over time. Given such a modestly effective vaccine, it is unknown to what extent a universal vaccination campaign, or one that prioritizes key populations, will reduce overall HIV incidence in the population.

As part of a collaboration established by the Centers for Disease Control and Prevention (CDC) and the Joint United Nations Programme on HIV/AIDS (UNAIDS), we evaluated the health and economic outcomes resulting from broad use of a partially effective HIV vaccine in the United States. Our analysis assumed declining vaccine efficacy as observed in the RV144 trial. We evaluated three strategies: one-time vaccination; vaccination followed by booster vaccinations at three- or five-year intervals; and a hybrid strategy, in which sub-populations at higher risk of HIV exposure received booster vaccinations. We evaluated the effect of these strategies on HIV incidence, infections averted, life expectancy, quality-adjusted life expectancy, costs, and cost-effectiveness.

Section snippets

Methods

Applying our previously published HIV vaccine model [6], we incorporated the 2009 ALVAC/AIDSVAX randomized clinical trial results to consider the effects of such a modestly effective HIV vaccine on population health outcomes and cost-effectiveness [3]. Additional model details can be found elsewhere [6], [12]. The model was implemented in the mathematical programming language Matlab 2010b.

Results

With no HIV vaccination program, we estimated that approximately 590,000 new HIV infections will occur in the United States over the next 10 years, with 47% of cases occurring among MSM, 20% among PWID, 6% among MSM/PWID, and 27% among heterosexually exposed populations.

Discussion

In this model-based analysis for the United States, we estimated the population health and economic outcomes that would result from use of an HIV vaccine with efficacy similar to that observed in the RV144 trial. Over the three years of the RV144 trial, use of the vaccine reduced new infections by 31%. However, the efficacy of the vaccine was potentially higher during the first year and subsequently declined rapidly, and our analysis was designed to reflect this declining efficacy. Because of

Acknowledgements

This work was supported by a grant from the National Institute on Drug Abuse, United States National Institutes of Health (R-01-DA-15612) and the United States Department of Veterans Affairs.

Conflict of interest: Each author reports no conflict of interest or any external financial support that is relevant to this study. Funding: Our funding sources had no role in the design of the study, in the collection, analysis, and interpretation of data, in the writing of the manuscript, and in the

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