Background Asymptomatic SARS-CoV-2 infection in children is highly prevalent but its acute and chronic implications have been minimally described. Methods In this controlled case-ascertained household transmission study, we recruited asymptomatic children <18 years with SARS-CoV-2 nucleic acid testing performed at 12 tertiary care pediatric institutions in Canada and the United States. We attempted to recruit all test-positive children and 1 to 3 test-negative, site-matched controls. After 14 days’ follow-up we assessed the clinical (ie, symptomatic) and combined (ie, test-positive, or symptomatic) secondary attack rates (SARs) among household contacts. Additionally, post–COVID-19 condition (PCC) was assessed in SARS-CoV-2–positive participating children after 90 days’ follow-up. Results A total of 111 test-positive and 256 SARS-CoV-2 test-negative asymptomatic children were enrolled between January 2021 and April 2022. After 14 days, excluding households with co-primary cases, the clinical SAR among household contacts of SARS-CoV-2–positive and –negative index children was 10.6% (19/179; 95% CI: 6.5%–16.1%) and 2.0% (13/663; 95% CI: 1.0%–3.3%), respectively (relative risk = 5.4; 95% CI: 2.7–10.7). In households with a SARS-CoV-2–positive index child, age <5 years, being pre-symptomatic (ie, developed symptoms after test), and testing positive during Omicron and Delta circulation periods (vs earlier) were associated with increased clinical and combined SARs among household contacts. Among 77 asymptomatic SARS-CoV-2–infected children with 90-day follow-up, 6 (7.8%; 95% CI: 2.9%–16.2%) reported PCC. Conclusions Asymptomatic SARS-CoV-2–infected children, especially those <5 years, are important contributors to household transmission, with 1 in 10 exposed household contacts developing symptomatic illness within 14 days. Asymptomatic SARS-CoV-2–infected children may develop PCC.

中文翻译：

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无症状 SARS-CoV-2 感染儿童的家庭传播动态：一项多国对照病例确定的前瞻性研究

背景 儿童中无症状 SARS-CoV-2 感染非常普遍，但对其急性和慢性影响的描述却很少。方法 在这项对照病例确定的家庭传播研究中，我们招募了 18 岁以下的无症状儿童，并在加拿大和美国的 12 家三级保健儿科机构进行了 SARS-CoV-2 核酸检测。我们尝试招募所有测试呈阳性的儿童和 1 至 3 名测试呈阴性的、地点匹配的对照。 14 天的随访后，我们评估了家庭接触者的临床（即有症状）和综合（即测试阳性或有症状）继发发作率 (SAR)。此外，在 90 天的随访后，对 SARS-CoV-2 阳性参与儿童的 COVID-19 后状况 (PCC) 进行了评估。结果 2021 年 1 月至 2022 年 4 月期间，共有 111 名检测呈阳性和 256 名 SARS-CoV-2 检测呈阴性的无症状儿童入组。14 天后，排除有共同原发病例的家庭，SARS 家庭接触者的临床 SAR CoV-2 阳性和阴性指数儿童分别为 10.6% (19/179; 95% CI: 6.5%–16.1%) 和 2.0% (13/663; 95% CI: 1.0%–3.3%)（相对风险 = 5.4；95% CI：2.7–10.7）。在有 SARS-CoV-2 阳性儿童的家庭中，年龄 <5 岁、出现症状前（即测试后出现症状）以及在 Omicron 和 Delta 循环期间（与之前相比）测试呈阳性与增加家庭接触者中的临床和综合 SAR。在 90 天随访的 77 名无症状 SARS-CoV-2 感染儿童中，有 6 名（7.8%；95% CI：2.9%–16.2%）报告出现 PCC。结论 无症状 SARS-CoV-2 感染儿童，尤其是 5 岁以下儿童，是家庭传播的重要因素，十分之一的暴露家庭接触者在 14 天内出现症状。无症状 SARS-CoV-2 感染儿童可能会患上 PCC。