Futures Institute, 41-A New London Turnpike, Glastonbury, CT 06033, United States.
Vaccine. 2011 Aug 18;29(36):6092-9. doi: 10.1016/j.vaccine.2011.06.060. Epub 2011 Jun 22.
Although published data from the recent ALVAC/AIDSVAX trial in Thailand (RV144) indicated the HIV vaccine provided very modest protection overall (31.2%), new analysis of trial data has suggested higher efficacy levels earlier in the follow-up period. CDC and UNAIDS organized several modeling research teams to explore the implications of the trial results and potential utility of this vaccine.
We explored the impact of a vaccine with moderate but rapidly waning protection (78%, 1.43 years) using an exponential decay function fit to trial data. We varied program coverage levels (20-80%), vaccine efficacy (30-90%), timing (single or multi-year programs), targeting (general or populations at higher risk), and background levels of all other prevention programs (constant or scaled-up). We simulated these various vaccination scenarios in two representative countries using demographic projections generated with Spectrum modeling software. We assumed the vaccine becomes available in 2020 and target coverage is achieved by 2025.
A general vaccination strategy in South Africa covering 60% of the population, for example, would prevent 3.0 million infections between 2020 and 2030-36% of expected infections-and would be very effective, requiring only 39 vaccinations/infection averted. The same strategy in Thailand would prevent 81,000 infections-35% of expected infections-but would require 1725 vaccinations/infection averted. Targeting only populations at higher risk of exposure in Thailand would reduce total vaccinations given by more than ten-fold and would still prevent 52,000 infections-23% of expected infections-while requiring only 220 vaccinations/infection averted. Outcomes were sensitive to program coverage, vaccine efficacy and background levels of all other prevention programs.
A vaccine with rapidly waning protection could have a substantial impact on the epidemic in South Africa and Thailand. Due to the short duration of effect, large numbers of vaccinations would be needed to maintain high population coverage levels. Further research into the immunological effects of booster vaccinations is warranted.
尽管最近泰国（RV144）的 ALVAC/AIDSVAX 试验发表的数据表明，该艾滋病毒疫苗总体上提供了非常适度的保护（31.2%），但对试验数据的新分析表明，在随访早期，疫苗的效果更高。美国疾病控制与预防中心和联合国艾滋病规划署组织了几个建模研究小组，以探讨试验结果的影响和该疫苗的潜在效用。
我们使用对试验数据进行拟合的指数衰减函数，探讨了具有中度但迅速减弱保护作用的疫苗（78%，1.43 年）的影响。我们改变了方案覆盖率（20-80%）、疫苗效力（30-90%）、时间（单年或多年方案）、目标人群（普通人群或高危人群）以及所有其他预防方案的背景水平（固定或扩大）。我们使用 Spectrum 建模软件生成的人口预测数据，在两个代表性国家模拟了这些不同的接种方案。我们假设疫苗在 2020 年上市，并在 2025 年实现目标覆盖。
例如，在南非实施针对普通人群、覆盖 60%人口的接种策略，将在 2020 年至 2030-2036 年期间预防 300 万例感染——占预期感染的 36%——且非常有效，每避免一例感染仅需接种 39 剂疫苗。在泰国实施同样的策略，将预防 81000 例感染——占预期感染的 35%——但需要接种 1725 剂疫苗/避免一例感染。仅针对泰国高危人群接种疫苗，将使接种疫苗的总人数减少 10 倍以上，仍可预防 52000 例感染——占预期感染的 23%——而每避免一例感染仅需接种 220 剂疫苗。结果对方案覆盖率、疫苗效力和所有其他预防方案的背景水平均敏感。
具有迅速减弱保护作用的疫苗可能对南非和泰国的疫情产生重大影响。由于作用持续时间短，需要大量接种疫苗以维持高人群覆盖率。有必要进一步研究加强免疫接种的免疫效果。
