Klimek Peter, Ledebur Katharina, Thurner Stefan
Section for Science of Complex Systems, Medical University of Vienna, Vienna, Austria.
Complexity Science Hub Vienna, Vienna, Austria.
Commun Med (Lond). 2024 Jul 7;4(1):134. doi: 10.1038/s43856-024-00561-4.
The effectiveness of non-pharmaceutical interventions to control the spread of SARS-CoV-2 depends on many contextual factors, including adherence. Conventional wisdom holds that the effectiveness of protective behaviours, such as wearing masks, increases with the number of people who adopt them. Here we show in a simulation study that this is not always true.
We use a parsimonious network model based on the well-established empirical facts that adherence to such interventions wanes over time and that individuals tend to align their adoption strategies with their close social ties (homophily).
When these assumptions are combined, a broad dynamic regime emerges in which the individual-level reduction in infection risk for those adopting protective behaviour increases as adherence to protective behaviour decreases. For instance, at 10 % coverage, we find that adopters face nearly a 30 % lower infection risk than at 60 % coverage. Based on surgical mask effectiveness estimates, the relative risk reduction for masked individuals ranges from 5 % to 15 %, or a factor of three. This small coverage effect occurs when the outbreak is over before the pathogen is able to invade small but closely knit groups of individuals who protect themselves.
Our results confirm that lower coverage reduces protection at the population level while contradicting the common belief that masking becomes ineffective at the individual level as more people drop their masks.
非药物干预措施控制严重急性呼吸综合征冠状病毒2（SARS-CoV-2）传播的有效性取决于许多背景因素，包括依从性。传统观点认为，诸如佩戴口罩等保护行为的有效性会随着采取这些行为的人数增加而提高。在此，我们通过一项模拟研究表明情况并非总是如此。
我们使用一个简约的网络模型，该模型基于已确立的实证事实，即对这类干预措施的依从性会随着时间推移而减弱，且个体倾向于使其采用策略与其紧密的社会关系（同质性）保持一致。
当这些假设结合在一起时，会出现一种广泛的动态模式，即采取保护行为的个体层面感染风险降低幅度会随着对保护行为依从性的降低而增加。例如，在覆盖率为10%时，我们发现采取保护行为者面临的感染风险比覆盖率为60%时低近30%。根据外科口罩有效性估计，佩戴口罩个体的相对风险降低幅度在5%至15%之间，即相差三倍。当疫情在病原体能够侵入自我保护的小型紧密群体之前结束时，就会出现这种小覆盖率效应。
我们的结果证实，较低的覆盖率会在人群层面降低保护效果，同时与一种普遍观念相矛盾，即随着更多人摘下口罩，在个体层面戴口罩会变得无效。
