Though recent reports link SARS-CoV-2 infections with hyper-inflammatory states in children, most children experience no/mild symptoms, and hospitalization and mortality rates are low in the age group. As symptoms are usually mild and seroconversion occurs at low frequencies, it remains unclear whether children significantly contribute to community transmission. Several hypotheses try to explain age-related differences in disease presentation and severity. Possible reasons for milder presentations in children as compared to adults include frequent contact to seasonal coronaviruses, presence of cross-reactive antibodies, and/or co-clearance with other viruses. Increased expression of ACE2 in young people may facilitate virus infection, while limiting inflammation and reducing the risk of severe disease. Further potential factors include recent vaccinations and a more diverse memory T cell repertoire. This manuscript reviews age-related host factors that may protect children from COVID-19 and complications associated, and addresses the confusion around seropositivity and immunity.

尽管最近的报告将 SARS-CoV-2 感染与儿童的过度炎症状态联系起来，但大多数儿童没有症状/症状较轻，而且该年龄组的住院率和死亡率都很低。由于症状通常较轻且发生血清转化的频率较低，因此尚不清楚儿童是否对社区传播有显着贡献。一些假设试图解释疾病表现和严重程度的年龄相关差异。与成人相比，儿童表现较轻的可能原因包括经常接触季节性冠状病毒、存在交叉反应抗体和/或与其他病毒共同清除。年轻人中 ACE2 表达的增加可能会促进病毒感染，同时限制炎症并降低患严重疾病的风险。其他潜在因素包括最近的疫苗接种和更多样化的记忆 T 细胞库。这份手稿回顾了可能保护儿童免受 COVID-19 和相关并发症的年龄相关宿主因素，并解决了血清阳性和免疫方面的混淆。