Shanghai Institute of Infectious Disease and Biosecurity, School of Public Health, Fudan University, Shanghai, China.
Department of Infectious Disease Control and Prevention, Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
BMJ Glob Health. 2023 Dec 22;8(12):e012289. doi: 10.1136/bmjgh-2023-012289.
We analysed case-contact clusters during the Omicron BA.2 epidemic in Shanghai to assess the risk of infection of contacts in different settings and to evaluate the effect of demographic factors on the association of infectivity and susceptibility to the Omicron variant.
Data on the settings and frequency of contact, demographic characteristics and comorbidities of index cases, contacts and secondary cases were analysed. Independent effect of multiple variables on the risk for transmission and infection was evaluated using generalised estimating equations.
From 1 March to 1 June 2022, we identified 450 770 close contacts of 90 885 index cases. The risk for infection was greater for contacts in farmers' markets (fixed locations where farmers gather to sell products, adjusted OR (aOR): 3.62; 95% CI 2.87 to 4.55) and households (aOR: 2.68; 95% CI 2.15 to 3.35). Children (0-4 years) and elderly adults (60 years and above) had higher risk for infection and transmission. During the course of the epidemic, the risk for infection and transmission in different age groups initially increased, and then decreased on about 21 April (17th day of citywide home quarantine). Compared with medical workers (reference, aOR: 1.00), unemployed contacts (aOR: 1.77; 95% CI 1.53 to 2.04) and preschoolers (aOR: 1.61; 95% CI 1.26 to 2.05) had the highest risk for infection; delivery workers (aOR: 1.90, 95% CI 1.51 to 2.40) and public service workers (aOR: 1.85; 95% CI 1.64 to 2.10) had the highest risk for transmission. Contacts who had comorbidities (aOR: 1.10; 95% CI 1.09 to 1.12) had a higher risk for infection, particularly those with lung diseases or immune deficiency.
Farmers' markets and households were the main setting for transmission of Omicron. Children, the elderly, delivery workers and public service workers had the highest risk for transmission and infection. These findings should be considered when implementing targeted interventions.
我们分析了奥密克戎 BA.2 疫情期间的病例接触者聚集情况，以评估不同环境下接触者感染的风险，并评估人口统计学因素对奥密克戎变异株传染性和易感性关联的影响。
分析了索引病例、接触者和二级病例的设置和接触频率、人口统计学特征和合并症的数据。使用广义估计方程评估多个变量对传播和感染风险的独立影响。
从 2022 年 3 月 1 日至 6 月 1 日，我们共确定了 90885 例索引病例的 450770 名密切接触者。在农贸市场（农民聚集销售产品的固定场所）和家庭（调整后的 OR（aOR）：3.62；95%CI 2.87 至 4.55）中，接触者的感染风险更高。儿童（0-4 岁）和老年人（60 岁及以上）的感染和传播风险更高。在疫情期间，不同年龄段的感染和传播风险最初呈上升趋势，然后在大约 4 月 21 日（全市居家隔离的第 17 天）下降。与医务人员（参照组，aOR：1.00）相比，失业接触者（aOR：1.77；95%CI 1.53 至 2.04）和学龄前儿童（aOR：1.61；95%CI 1.26 至 2.05）感染风险最高；送货员（aOR：1.90，95%CI 1.51 至 2.40）和公共服务人员（aOR：1.85；95%CI 1.64 至 2.10）的传播风险最高。有合并症的接触者（aOR：1.10；95%CI 1.09 至 1.12）感染风险更高，尤其是患有肺部疾病或免疫缺陷的接触者。
农贸市场和家庭是奥密克戎传播的主要场所。儿童、老年人、送货员和公共服务人员的传播和感染风险最高。在实施有针对性的干预措施时，应考虑这些发现。
