BACKGROUND Studies on age-related differences in clinical and laboratory features of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are limited. We aimed to evaluate the demographic, clinical, laboratory findings of SARS-CoV-2 infection in children younger than 6 months old and compare them with older children. METHODS A single-center retrospective study, including 209 confirmed SARS-CoV-2 infection cases, was conducted between 11 March 2020 and 1 September 2021. The case group consisted of 47 patients younger than 6 months old, whereas the control group consisted of 162 patients older than 6 months old. RESULTS The mean age of the case group was 2.77 ± 1.52 months, and the control group was 101.89 ± 65.77 months. Cough was statistically higher in the control group, and poor feeding was higher in the case group (p = 0.043, 0.010). The underlying disease rate was statistically higher in the control group; however, the hospitalization rate was higher in the case group (p = 0.036, 0.001). The case group had significantly lower median values of the absolute neutrophil count, hemoglobin and higher median values of white blood cell, absolute lymphocyte count and platelet than the control group (p < 0.05). C-reactive protein, fibrinogen values were significantly lower, and procalcitonin, D-dimer, troponin T, N-terminal pro-B-type natriuretic peptide significantly higher in the case group (p < 0.05). Lymphopenia was more common in the control group, whereas neutropenia was more common in the case group (p = 0.001, 0.011). CONCLUSIONS We showed that most children younger than 6 months old had mild and asymptomatic SARS-CoV-2 infection; however, the hospitalization rate was higher, and neutropenia was more common in older children. Lay summaryStudies on age-related differences in clinical and laboratory features on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in pediatric patients are limited. We aimed to evaluate the demographic, clinical and laboratory findings of SARS-CoV-2 infection in children younger than 6 months old and compare them with older children. A single-center retrospective study was conducted, including 209 SARS-CoV-2 infection cases. The case group consisted of 47 patients younger than 6 months old, and the control group consisted of 162 patients older than 6 months old. Most children younger than 6 months old had mild and asymptomatic SARS-CoV-2 infection; however, the hospitalization rate was higher than older children. Neutropenia was more common in patients younger than 6 months than older children with SARS-CoV-2 infection, even if underlying diseases were excluded.

中文翻译：

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6 个月以下儿童感染 SARS-CoV-2 的临床和实验室发现：中性粒细胞减少症比淋巴细胞减少症更常见。

背景关于严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染的临床和实验室特征的年龄相关差异的研究有限。我们旨在评估 6 个月以下儿童感染 SARS-CoV-2 的人口统计学、临床和实验室结果，并将其与年龄较大的儿童进行比较。方法 2020 年 3 月 11 日至 2021 年 9 月 1 日期间，对 209 例确诊的 SARS-CoV-2 感染病例进行了一项单中心回顾性研究。病例组由 47 名小于 6 个月的患者组成，而对照组由 162 名患者组成。 6个月以上的患者。结果病例组平均年龄2.77±1.52个月，对照组101.89±65.77个月。对照组的咳嗽率在统计学上更高，而病例组的喂养不良率更高（p = 0.043，0.010)。对照组的基础疾病发生率在统计学上更高；然而，病例组的住院率更高（p = 0.036, 0.001）。病例组中性粒细胞绝对计数、血红蛋白的中位数明显低于对照组，白细胞、淋巴细胞绝对计数和血小板的中位数高于对照组（p < 0.05）。病例组C反应蛋白、纤维蛋白原值显着降低，降钙素原、D-二聚体、肌钙蛋白T、N端B型利钠肽原显着升高（p < 0.05）。淋巴细胞减少症在对照组中更为常见，而中性粒细胞减少症在病例组中更为常见（p = 0.001, 0.011）。结论 我们发现，大多数小于 6 个月大的儿童患有轻度和无症状的 SARS-CoV-2 感染；然而，住院率较高，中性粒细胞减少症在年龄较大的儿童中更为常见。总结关于儿童患者严重急性呼吸系统综合征冠状病毒 2 (SARS-CoV-2) 感染的临床和实验室特征的年龄相关差异的研究是有限的。我们旨在评估 6 个月以下儿童感染 SARS-CoV-2 的人口统计学、临床和实验室结果，并将其与年龄较大的儿童进行比较。进行了一项单中心回顾性研究，包括 209 例 SARS-CoV-2 感染病例。病例组包括 47 名小于 6 个月的患者，对照组包括 162 名大于 6 个月的患者。大多数 6 个月以下的儿童感染了轻微且无症状的 SARS-CoV-2；然而，住院率高于年龄较大的儿童。