Futures Institute, Glastonbury, Connecticut, United States of America.
PLoS One. 2010 Nov 5;5(11):e13646. doi: 10.1371/journal.pone.0013646.
Mathematical modelers have given little attention to the question of how pre-exposure prophylaxis (PrEP) may impact on a generalized national HIV epidemic and its cost-effectiveness, in the context of control strategies such as condom use promotion and expanding ART programs.
METHODOLOGY/PRINCIPAL FINDINGS: We use an age- and gender-structured model of the generalized HIV epidemic in South Africa to investigate the potential impact of PrEP in averting new infections. The model utilizes age-structured mortality, fertility, partnership and condom use data to model the spread of HIV and the shift of peak prevalence to older age groups. The model shows that universal PrEP coverage would have to be impractically high to have a significant effect on incidence reduction while ART coverage expands. PrEP targeted to 15-35-year-old women would avert 10%-25% (resp. 13%-28%) of infections in this group and 5%-12% (resp. 7%-16%) of all infections in the period 2014-2025 if baseline incidence is 0.5% per year at 2025 (resp. 0.8% per year at 2025). The cost would be $12,500-$20,000 per infection averted, depending on the level of ART coverage and baseline incidence. An optimistic scenario of 30%-60% PrEP coverage, efficacy of at least 90%, no behavior change among PrEP users and ART coverage less than three times its 2010 levels is required to achieve this result. Targeting PrEP to 25-35-year-old women (at highest risk of infection) improves impact and cost-effectiveness marginally. Relatively low levels of condom substitution (e.g., 30%) do not nullify the efficacy of PrEP, but reduces cost-effectiveness by 35%-40%.
CONCLUSIONS/SIGNIFICANCE: PrEP can avert as many as 30% of new infections in targeted age groups of women at highest risk of infection. The cost-effectiveness of PrEP relative to ART decreases rapidly as ART coverage increases beyond three times its coverage in 2010, after which the ART program would provide coverage to more than 65% of HIV(+) individuals. To have a high relative cost-effective impact on reducing infections in generalized epidemics, PrEP must utilize a window of opportunity until ART has been scaled up beyond this level.
在推广使用安全套和扩大抗逆转录病毒疗法（ART）项目等控制策略的背景下，数学模型专家很少关注事前预防（PrEP）可能对普遍存在的全国艾滋病毒流行及其成本效益产生的影响。
方法/主要发现：我们使用南非普遍存在的艾滋病毒流行的年龄和性别结构模型，研究 PrEP 在预防新感染方面的潜在影响。该模型利用年龄结构死亡率、生育率、伙伴关系和安全套使用数据来模拟艾滋病毒的传播以及流行高峰期向老年群体的转移。模型表明，要想在扩大 ART 覆盖范围的同时，对发病率降低产生重大影响，普遍的 PrEP 覆盖率将不得不高得离谱。针对 15-35 岁女性的 PrEP 可预防该人群中 10%-25%（分别为 13%-28%）的感染，以及 2014-2025 年期间所有感染的 5%-12%（分别为 7%-16%），如果 2025 年的基础发病率为每年 0.5%（分别为每年 0.8%）。成本将为每例感染预防 12500-20000 美元，具体取决于 ART 覆盖率和基础发病率。需要达到 30%-60%的 PrEP 覆盖率、至少 90%的疗效、PrEP 用户行为没有变化以及 ART 覆盖率低于其 2010 年水平的三倍，才能实现这一结果。将 PrEP 针对感染风险最高的 25-35 岁女性（风险最高的感染人群），可以略微提高效果和成本效益。相对较低水平的 condom 替代率（例如 30%）不会使 PrEP 的疗效失效，但会使成本效益降低 35%-40%。
结论/意义：PrEP 可以预防感染风险最高的目标年龄组的女性中多达 30%的新感染。随着 ART 覆盖率超过 2010 年的三倍，PrEP 的成本效益相对于 ART 迅速降低，之后 ART 项目将为超过 65%的 HIV（+）个体提供覆盖。为了在普遍流行中对减少感染产生高相对成本效益的影响，PrEP 必须利用机会之窗，直到 ART 扩大到这一水平以上。
