COVID-19 Case Rates in the UK: Modelling Uncertainties as Lockdown Lifts
COVID-19 Case Rates in the UK: Modelling Uncertainties as Lockdown Lifts
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DOI：
10.3390/systems9030060
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发表时间：
2021-09-01
期刊：
影响因子：
1.9
通讯作者：
Pedercini, Matteo
中科院分区：
文献类型：
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作者：
Brereton, Claire;Pedercini, Matteo
背景：英国是欧洲受COVID-19疫情影响最严重的国家之一。自二零二一年初起实施的严格封城措施，加上积极的疫苗接种计划，令封城措施得以逐步放宽，而死亡及呈报个案数目均减少至高峰期的3%以下。2021年4月Delta变异病毒的出现扭转了这一趋势，英国再次出现病例激增，尽管由于疫苗接种的成功推广，平均严重程度有所降低。这项研究提出了一项模拟工作的结果，该工作通过预测封锁解除时的每日病例数来模拟英国大流行的进展。方法：建立基于易感-暴露-暴露-覆盖结构的仿真模型。英国封锁措施的时间轴用于模拟不断变化的限制。该模型是为英国量身定制的，其中一些值是根据研究设定的，其他值是通过16个月的历史数据校准获得的。结果如下：该模型预测，倘于二零二一年七月解除封锁限制，英国COVID-19病例将于最可行的情况下达到每日数十万例的高峰，并于二零二一年年底减少，原因是透过疫苗接种及感染获得的免疫力降低了易感人群的百分比。进一步的封锁措施可用于减少日常病例。除了不断出现新变种的威胁外，影响英国大流行概况的最重要未知因素是免疫力的持续时间和强度，如果免疫力持续8个月，每日高峰病例将比12个月高出50%以上。另一个重要因素是未报告案件的百分比。与疫苗接种相关的病例严重程度降低可能导致未报告的轻度或无症状病例比例增加，这意味着未知病例导致的未管理感染将继续成为主要感染源。结论：进一步研究恢复和接种COVID-19免疫力的长度和强度对于从模型中提供更准确的预测至关重要，从而能够做出更精细的政策决策。本文中提出的模型虽然并不完美，但旨在提高建模过程的透明度，这只会增加政策制定者，记者和公众之间的信任。
Background: The UK was one of the countries worst affected by the COVID-19 pandemic in Europe. A strict lockdown from early 2021 combined with an aggressive vaccination programme enabled a gradual easing of lockdown measures to be introduced whilst both deaths and reported case numbers reduced to less than 3% of their peak. The emergence of the Delta variant in April 2021 has reversed this trend, and the UK is once again experiencing surging cases, albeit with reduced average severity due to the success of the vaccination rollout. This study presents the results of a modelling exercise which simulates the progression of the pandemic in the UK through projection of daily case numbers as lockdown lifts. Methods: A simulation model based on the Susceptible-Exposed-Infected-Recovered structure was built. A timeline of UK lockdown measures was used to simulate the changing restrictions. The model was tailored for the UK, with some values set based on research and others obtained through calibration against 16 months of historical data. Results: The model projects that if lockdown restrictions are lifted in July 2021, UK COVID-19 cases will peak at hundreds of thousands daily in most viable scenarios, reducing in late 2021 as immunity acquired through both vaccination and infection reduces the susceptible population percentage. Further lockdown measures can be used to reduce daily cases. Other than the ever-present threat of the emergence of new variants, the most significant unknown factors affecting the profile of the pandemic in the UK are the length and strength of immunity, with daily peak cases over 50% higher if immunity lasts 8 months compared to 12 months. Another significant factor is the percentage of unreported cases. The reduced case severity associated with vaccination may lead to a higher proportion of unreported mild or asymptomatic cases, meaning that unmanaged infections resulting from unknown cases will continue to be a major source of infection. Conclusions: Further research into the length and strength of both recovered and vaccinated COVID-19 immunity is critical to delivering more accurate projections from models, thus enabling more finely tuned policy decisions. The model presented in this article, whilst by no means perfect, aims to contribute to greater transparency of the modelling process, which can only increase trust between policy makers, journalists and the general public.