Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; Covid Crisis Lab, Bocconi University, Italy; Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; Department of Network and Data Science, Central European University, Wien, Austria.
Epidemics. 2022 Sep;40:100601. doi: 10.1016/j.epidem.2022.100601. Epub 2022 Jun 17.
After a rapid upsurge of COVID-19 cases in Italy during the fall of 2020, the government introduced a three-tiered restriction system aimed at increasing physical distancing. The Ministry of Health, after periodic epidemiological risk assessments, assigned a tier to each of the 21 Italian regions and autonomous provinces. It is still unclear to what extent these different sets of measures altered the number of daily interactions and the social mixing patterns.
We conducted a survey between July 2020 and March 2021 to monitor changes in social contact patterns among individuals in the metropolitan city of Milan, Italy, which was hardly hit by the second wave of the COVID-19 pandemic. The number of daily contacts during periods characterized by different levels of restrictions was analyzed through negative binomial regression models and age-specific contact matrices were estimated under the different tiers of restrictions. By relying on the empirically estimated mixing patterns, we quantified relative changes in SARS-CoV-2 transmission potential associated with the different tiers. As tighter restrictions were implemented during the fall of 2020, a progressive reduction in the mean number of daily contacts recorded by study participants was observed: from 15.9 % under mild restrictions (yellow tier), to 41.8 % under strong restrictions (red tier). Higher restrictions levels were also found to increase the relative contribution of contacts occurring within the household. The SARS-CoV-2 reproduction number was estimated to decrease by 17.1 % (95 %CI: 1.5-30.1), 25.1 % (95 %CI: 13.0-36.0) and 44.7 % (95 %CI: 33.9-53.0) under the yellow, orange, and red tiers, respectively.
Our results give an important quantification of the expected contribution of different restriction levels in shaping social contacts and decreasing the transmission potential of SARS-CoV-2. These estimates can find an operational use in anticipating the effect that the implementation of these tiered restriction can have on SARS-CoV-2 reproduction number under an evolving epidemiological situation.
2020 年秋季，意大利 COVID-19 病例迅速增加，政府推出了三级限制制度，旨在增加身体距离。卫生部在定期进行流行病学风险评估后，为意大利的 21 个地区和自治区分配了一个级别。目前尚不清楚这些不同的措施在多大程度上改变了每日互动的数量和社会混合模式。
我们在 2020 年 7 月至 2021 年 3 月期间进行了一项调查，以监测意大利米兰大都市区个体社会接触模式的变化，米兰在 COVID-19 疫情的第二波中几乎没有受到影响。通过负二项回归模型分析了在不同限制水平下，每天接触的次数，在不同的限制级别下，还估计了特定年龄的接触矩阵。通过依赖经验估计的混合模式，我们量化了与不同级别相关的 SARS-CoV-2 传播潜力的相对变化。随着 2020 年秋季限制措施的加强，研究参与者记录的每日平均接触次数逐渐减少：从轻度限制（黄色级别）下的 15.9%减少到严格限制（红色级别）下的 41.8%。较高的限制水平也被发现增加了家庭内发生的接触的相对贡献。估计 SARS-CoV-2 的繁殖数在黄色、橙色和红色级别下分别减少了 17.1%（95%CI：1.5-30.1）、25.1%（95%CI：13.0-36.0）和 44.7%（95%CI：33.9-53.0）。
我们的结果对不同限制水平在塑造社会接触和降低 SARS-CoV-2 传播潜力方面的预期贡献进行了重要量化。这些估计可以在预测实施这些分层限制对 SARS-CoV-2 繁殖数的影响方面发挥作用，这在不断变化的流行病学情况下。
