DSI-NRF Centre of Excellence in Epidemiological Modelling and Analysis, Stellenbosch University, Stellenbosch, South Africa.
Access Campaign, Médecins Sans Frontières, New York, United States.
Vaccine. 2021 Sep 24;39(40):5845-5853. doi: 10.1016/j.vaccine.2021.08.053. Epub 2021 Sep 1.
Rapid outbreak response vaccination is a strategy for measles control and elimination. Measles vaccines must be stored and transported within a specified temperature range, but this can present significant challenges when targeting remote populations. Measles vaccine licensure for delivery outside cold chain (OCC) could provide more vaccine transport/storage space without ice packs, and a solution to shorten response times. However, due to vaccine safety and wastage considerations, the OCC strategy will require other operational changes, potentially including the use of 1-dose (monodose) instead of 10-dose vials, requiring larger transport/storage equipment currently achieved with 10-dose vials. These trade-offs require quantitative comparisons of vaccine delivery options to evaluate their relative benefits.
We developed a modelling framework combining elements of the vaccine supply chain - cold chain, vial, team, and transport equipment types - with a measles transmission dynamics model to compare vaccine delivery options. We compared 10 strategies resulting from combinations of the vaccine supply elements and grouped into three main classes: OCC, partial cold chain (PCC), and full cold chain (FCC). For each strategy, we explored a campaign with 20 teams sequentially targeting 5 locations with 100,000 individuals each. We characterised the time needed to freeze ice packs and complete the campaign (campaign duration), vaccination coverage, and cases averted, assuming a fixed pre-deployment delay before campaign commencement. We performed sensitivity analyses of the pre-deployment delay, population sizes, and two team allocation schemes.
The OCC, PCC, and FCC strategies achieve campaign durations of 50, 51, and 52 days, respectively. Nine of the ten strategies can achieve a vaccination coverage of 80%, and OCC averts the most cases.
The OCC strategy, therefore, presents improved operational and epidemiological outcomes relative to current practice and the other options considered.
快速爆发应对疫苗接种是控制和消除麻疹的一种策略。麻疹疫苗必须在特定的温度范围内储存和运输，但对于偏远地区的人群来说，这可能会带来很大的挑战。在冷链之外（OCC）批准麻疹疫苗可以提供更多的疫苗运输/储存空间，而无需冰袋，并且可以缩短应对时间。然而，由于疫苗安全性和浪费的考虑，OCC 策略将需要其他操作上的改变，可能包括使用单剂量（单剂量）而不是 10 剂量小瓶，这需要更大的运输/储存设备，而目前使用 10 剂量小瓶可以实现。这些权衡需要对疫苗接种方案进行定量比较，以评估它们的相对益处。
我们开发了一个建模框架，将疫苗供应链的各个元素——冷链、小瓶、团队和运输设备类型——与麻疹传播动力学模型相结合，以比较疫苗接种方案。我们比较了 10 种由疫苗供应要素组合而成的策略，并将其分为三类：OCC、部分冷链（PCC）和全冷链（FCC）。对于每种策略，我们都探索了一个由 20 个团队组成的运动，这些团队依次针对 5 个地点，每个地点有 10 万人。我们描述了冻结冰袋和完成运动（运动持续时间）所需的时间、接种覆盖率和避免的病例，假设在运动开始前有一个固定的预先部署延迟。我们对预先部署延迟、人口规模和两种团队分配方案进行了敏感性分析。
OCC、PCC 和 FCC 策略的运动持续时间分别为 50、51 和 52 天。十种策略中有九种可以达到 80%的接种覆盖率，而 OCC 可以避免最多的病例。
因此，与当前做法和考虑的其他方案相比，OCC 策略提供了改进的运营和流行病学结果。
