Background

The extent to which very young children contribute to the transmission of SARS-CoV-2 is unclear. We aimed to estimate the seroprevalence of antibodies against SARS-CoV-2 in daycare centres that remained open for key workers' children during a nationwide lockdown in France.

Methods

Children and staff who attended one of 22 daycare centres during a nationwide lockdown in France (between March 15 and May 9, 2020) were included in this cross-sectional, multicentre, seroprevalence study. Hospital staff not occupationally exposed to patients with COVID-19, or to children, were enrolled in a comparator group. The primary outcome was SARS-CoV-2 seroprevalence in children, daycare centre staff, and the comparator group. The presence of antibodies against SARS-CoV-2 in capillary whole blood was measured with a rapid chromatographic immunoassay. We computed raw prevalence as the percentage of individuals with a positive IgG or IgM test, and used Bayesian smoothing to account for imperfect sensitivity and specificity of the assay. This study is registered with ClinicalTrials.gov, NCT04413968.

Findings

Between June 4 and July 3, 2020, we enrolled 327 children (mean age 1·9 [SD 0·9] years; range 5 months to 4·4 years), 197 daycare centre staff (mean age 40 [12] years), and 164 adults in the comparator group (42 [12] years). Positive serological tests were observed for 14 children (raw seroprevalence 4·3%; 95% CI 2·6–7·1) and 14 daycare centre staff (7·7%; 4·2–11·6). After accounting for imperfect sensitivity and specificity of the assay, we estimated that 3·7% (95% credible interval [95% CrI] 1·3–6·8) of the children and 6·8% (3·2–11·5) of daycare centre staff had SARS-CoV-2 infection. The comparator group fared similarly to the daycare centre staff; nine participants had a positive serological test (raw seroprevalence 5·5%; 95% CI 2·9–10·1), leading to a seroprevalence of 5·0% (95% CrI 1·6–9·8) after accounting for assay characteristics. An exploratory analysis suggested that seropositive children were more likely than seronegative children to have been exposed to an adult household member with laboratory-confirmed COVID-19 (six [43%] of 14 vs 19 [6%] of 307; relative risk 7·1 [95% CI 2·2–22·4]).

Interpretation

According to serological test results, the proportion of young children in our sample with SARS-CoV-2 infection was low. Intrafamily transmission seemed more plausible than transmission within daycare centres. Further epidemiological studies are needed to confirm this exploratory hypothesis.

Funding

Assistance Publique—Hôpitaux de Paris; Mairie de Paris, Conseil Départemental de Seine Saint Denis.

Translations

For the French translation of the abstract see Supplementary Materials section.

中文翻译：

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法国全国封锁期间日托中心儿童和工作人员中的 SARS-CoV-2 传播：一项横断面、多中心、血清流行率研究

 背景

幼儿对 SARS-CoV-2 传播的影响程度尚不清楚。我们的目的是估计在法国全国封锁期间，日托中心仍然对关键工人的子女开放的日托中心中 SARS-CoV-2 抗体的血清阳性率。

 方法

这项横断面、多中心血清阳性率研究纳入了法国全国封锁期间（2020 年 3 月 15 日至 5 月 9 日）期间到 22 个日托中心之一就读的儿童和工作人员。未因职业接触 COVID-19 患者或儿童的医院工作人员被纳入对照组。主要结果是儿童、日托中心工作人员和对照组的 SARS-CoV-2 血清流行率。通过快速色谱免疫分析检测毛细血管全血中是否存在针对 SARS-CoV-2 的抗体。我们将原始患病率计算为 IgG 或 IgM 检测呈阳性的个体的百分比，并使用贝叶斯平滑来解释检测的不完善的灵敏度和特异性。本研究已在 ClinicalTrials.gov 注册，NCT04413968。

 发现

2020 年 6 月 4 日至 7 月 3 日期间，我们招募了 327 名儿童（平均年龄 1·9 [SD 0·9] 岁；范围 5 个月至 4·4 岁）、197 名日托中心工作人员（平均年龄 40 [12] 岁） ，以及比较组中的 164 名成年人（42 [12] 岁）。 14 名儿童（原始血清阳性率 4·3%；95% CI 2·6–7·1）和 14 名日托中心工作人员（7·7%；4·2–11·6）的血清学检测呈阳性。考虑到检测的不完善的敏感性和特异性后，我们估计 3·7%（95% 可信区间 [95% CrI]1·3–6·8）的儿童和 6·8%（3·2–11） ·5) 的日托中心工作人员感染了 SARS-CoV-2。比较组的表现与日托中心工作人员相似；九名参与者的血清学检测呈阳性（原始血清阳性率为 5·5%；95% CI 2·9–10·1），统计后血清阳性率为 5·0%（95% CrI 1·6–9·8）用于测定特性。一项探索性分析表明，血清反应呈阳性的儿童比血清反应呈阴性的儿童更有可能接触过实验室确诊的 COVID-19 的成年家庭成员（14 人中的 6 人 [43%] vs 307 人中的 19 人 [6%]；相对风险 7· 1 [95% CI 2·2–22·4]）。

 解释

根据血清学检测结果，我们样本中幼儿感染SARS-CoV-2的比例较低。家庭内传播似乎比日托中心内传播更合理。需要进一步的流行病学研究来证实这一探索性假设。

 资金

公共援助——巴黎医院；巴黎市政厅，塞纳圣但尼省议会。

 翻译

有关摘要的法文翻译，请参阅补充材料部分。