Clinical and Laboratory Findings of SARS-CoV-2 Infection in Children Younger than 6 Months Old: Neutropenia is More Common Not Lymphopenia

Abstract 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 summary Studies 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 ra