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Household transmission of SARS-CoV-2 during the Omicron wave in Shanghai, China:a case-ascertained study
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  • Zhongqiu Wei,
  • Wenjie Ma,
  • Zhonglin Wang,
  • Jingjing Li,
  • Xiaomin Fu,
  • Hailing Chang,
  • Yue Qiu,
  • He Tian,
  • Yanfeng Zhu,
  • Aimei Xia,
  • Qianhui Wu,
  • Gongbao Liu ,
  • Xiaowen Zhai,
  • Xiaobo Zhang,
  • Yan Wang,
  • Mei Zeng
Zhongqiu Wei
Children's Hospital of Fudan University

Corresponding Author:zqwei0563@163.com

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Wenjie Ma
Children's Hospital of Fudan University
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Zhonglin Wang
Children's Hospital of Fudan University
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Jingjing Li
Children's Hospital of Fudan University
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Xiaomin Fu
Children's Hospital of Fudan University
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Hailing Chang
Children's Hospital of Fudan University
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Yue Qiu
Children's Hospital of Fudan University
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He Tian
Children's Hospital of Fudan University
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Yanfeng Zhu
Children's Hospital of Fudan University
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Aimei Xia
Children's Hospital of Fudan University
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Qianhui Wu
Fudan University School of Public Health
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Gongbao Liu
Children's Hospital of Fudan University
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Xiaowen Zhai
Children's Hospital of Fudan University
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Xiaobo Zhang
Children's Hospital of Fudan University
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Yan Wang
Fudan University School of Public Health
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Mei Zeng
Children's Hospital of Fudan University
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Abstract

Since late 2021, the highly transmissible SARS-CoV-2 Omicron variant has driven a new surge of infections across the world. We used a case-ascertained study to determine the features of household transmission of SARS-CoV-2 Omicron variant in Shanghai, China. We collected detailed information on 323 pediatric cases and their 951 household members, all received consecutively intensive RT-PCR testing. We estimated the transmission parameters. Both secondary infection attack rates (SARI) and secondary clinical attack rates (SARC) among adult household contacts were computed, through which the transmission heterogeneities in infectivity and susceptibility were characterized and the vaccine effectiveness were estimated. The mean incubation period and serial interval of Omicron variant were estimated to be 4.6±2.1 days and 3.9±3.7 days. The overall SARI and SARC among adult household contacts were 77.11% (95% confidence interval [CI]: 73.58%-80.63%) and 67.03% (63.09%-70.98%). We found higher household susceptibility in females, while infectivity was not significantly different in primary cases by age, sex, vaccination status and clinical severity. Full vaccination and booster vaccination of inactivated vaccines were 14.8% (5.8%-22.9%) and 18.9% (9.0%-27.7%) effective against Omicron infection and 21.5% (10.4%-31.2%) and 24.3% (12.3%-34.7%) effective against symptomatic disease. Overall, we found high household transmission during the Omicron wave in Shanghai due to asymptomatic and pre-symptomatic transmission in the context of city-wide lockdown, indicating the importance of early detection and timely isolation of SARS-CoV-2 infections and quarantine of close contacts. Marginal effectiveness of inactivated vaccines against Omicron infection poses great challenge for prevention and control of the SARS-CoV-2 Omicron variant.
28 Sep 2022Submitted to Influenza and other respiratory viruses
29 Sep 2022Submission Checks Completed
29 Sep 2022Assigned to Editor
06 Oct 2022Reviewer(s) Assigned
28 Nov 2022Review(s) Completed, Editorial Evaluation Pending
04 Dec 2022Editorial Decision: Revise Minor
01 Jan 20231st Revision Received
04 Jan 2023Submission Checks Completed
04 Jan 2023Assigned to Editor
04 Jan 2023Editorial Decision: Accept