Department of Microbiology, Faculty of Medicine, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
JAMA Netw Open. 2021 Nov 1;4(11):e2132923. doi: 10.1001/jamanetworkopen.2021.32923.
Seroprevalence studies inform the extent of infection and assist evaluation of mitigation strategies for the COVID-19 pandemic.
To estimate the prevalence of unidentified SARS-CoV-2 infection in the general population of Hong Kong.
DESIGN, SETTING, AND PARTICIPANTS: A prospective cross-sectional study was conducted in Hong Kong after each major wave of the COVID-19 pandemic (April 21 to July 7, 2020; September 29 to November 23, 2020; and January 15 to April 18, 2021). Adults (age ≥18 years) who had not been diagnosed with COVID-19 were recruited during each period, and their sociodemographic information, symptoms, travel, contact, quarantine, and COVID-19 testing history were collected.
The main outcome was prevalence of SARS-CoV-2 infection. SARS-CoV-2 IgG antibodies were detected by an enzyme-linked immunosorbent assay based on spike (S1/S2) protein, followed by confirmation with a commercial electrochemiluminescence immunoassay based on the receptor binding domain of spike protein.
The study enrolled 4198 participants (2539 [60%] female; median age, 50 years [IQR, 25 years]), including 903 (22%), 1046 (25%), and 2249 (53%) during April 21 to July 7, 2020; during September 29 to November 23, 2020; and during January 15 to April 18, 2021, respectively. The numbers of participants aged 18 to 39 years, 40 to 59 years, and 60 years or older were 1328 (32%), 1645 (39%), and 1225 (29%), respectively. Among the participants, 2444 (58%) stayed in Hong Kong since November 2019 and 2094 (50%) had negative SARS-CoV-2 RNA test results. Only 170 (4%) reported ever having contact with individuals with confirmed cases, and 5% had been isolated or quarantined. Most (2803 [67%]) did not recall any illnesses, whereas 737 (18%), 212 (5%), and 385 (9%) had experienced respiratory symptoms, gastrointestinal symptoms, or both, respectively, before testing. Six participants were confirmed to be positive for anti-SARS-CoV-2 IgG; the adjusted prevalence of unidentified infection was 0.15% (95% CI, 0.06%-0.32%). Extrapolating these findings to the whole population, there were fewer than 1.9 unidentified infections for every recorded confirmed case. The overall prevalence of SARS-CoV-2 infection in Hong Kong before the roll out of vaccination was less than 0.45%.
In this cross-sectional study of participants from the general public in Hong Kong, the prevalence of unidentified SARS-CoV-2 infection was low after 3 major waves of the pandemic, suggesting the success of the pandemic mitigation by stringent isolation and quarantine policies even without complete city lockdown. More than 99.5% of the general population of Hong Kong remain naive to SARS-CoV-2, highlighting the urgent need to achieve high vaccine coverage.
血清流行率研究可以反映感染程度，并有助于评估 COVID-19 大流行的缓解策略。
估计香港普通人群中未确诊的 SARS-CoV-2 感染的流行率。
设计、地点和参与者：这是一项在 COVID-19 大流行的每一波之后（2020 年 4 月 21 日至 7 月 7 日；2020 年 9 月 29 日至 11 月 23 日；2021 年 1 月 15 日至 4 月 18 日）在香港进行的前瞻性横断面研究。在每个时期招募未被诊断为 COVID-19 的成年人（年龄≥18 岁），收集他们的社会人口学信息、症状、旅行、接触、隔离和 COVID-19 检测史。
主要结果是 SARS-CoV-2 感染的流行率。通过基于刺突（S1/S2）蛋白的酶联免疫吸附试验检测 SARS-CoV-2 IgG 抗体，然后使用基于刺突蛋白受体结合域的商业电化学发光免疫分析进行确认。
该研究纳入了 4198 名参与者（2539 名[60%]为女性；中位年龄为 50 岁[IQR，25 岁]），其中 903 名（22%）、1046 名（25%）和 2249 名（53%）分别在 2020 年 4 月 21 日至 7 月 7 日、2020 年 9 月 29 日至 11 月 23 日和 2021 年 1 月 15 日至 4 月 18 日期间。参与者中年龄在 18 至 39 岁、40 至 59 岁和 60 岁或以上的人数分别为 1328 人（32%）、1645 人（39%）和 1225 人（29%）。其中，2444 人（58%）自 2019 年 11 月以来一直留在香港，2094 人（50%）SARS-CoV-2 RNA 检测结果为阴性。只有 170 人（4%）报告曾与确诊病例接触，5%的人曾被隔离或检疫。大多数（2803 人[67%]）没有回忆起任何疾病，而 737 人（18%）、212 人（5%）和 385 人（9%）在检测前分别出现呼吸症状、胃肠道症状或同时出现这些症状。有 6 名参与者被确认为抗 SARS-CoV-2 IgG 阳性；未确诊感染的调整流行率为 0.15%（95%CI，0.06%-0.32%）。将这些发现外推到整个人群，每记录的确诊病例不到 1.9 例未确诊感染。在疫苗接种推出之前，香港的 SARS-CoV-2 总体感染率低于 0.45%。
在这项针对香港普通人群的参与者的横断面研究中，在经历了 3 波大流行之后，未确诊的 SARS-CoV-2 感染的流行率较低，这表明即使没有完全的城市封锁，严格的隔离和检疫政策也成功地缓解了大流行。香港普通人群中超过 99.5%的人对 SARS-CoV-2 仍无免疫力，这突出表明迫切需要实现高疫苗接种率。
