Dear Editor,

We read with great interest the systematic review by Liguoro and colleagues (Volume 179, issue 7) [1]. The authors aimed to systematically review the main clinical characteristics and outcomes of SARS-CoV-2 infections in the pediatric age. We want to congratulate the authors for establishing a timely and informative systematic review of COVID-19 in children. Certainly, the findings of Liguoro et al. hold significance for pediatricians. However, we would like to draw their attention to the following issues.

First, we observed that the expression of “children with suspected or confirmed SARS-CoV-2 infection” has been mentioned several times. But the authors did not provide important information about “children with confirmed SARS-CoV-2 infection.” Did children with confirmed SARS-CoV-2 infection involve laboratory-confirmed and/or clinically diagnosed COVID-19? We hope that the authors can clarify the diagnostic methods and adopt a uniform case definition throughout the manuscript.

Furthermore, some children may have been included in multiple publications, as admission dates overlap for reports from the same hospital. The case series from reference 31 Sun et al. [2] should be considered a duplicate considering a large retrospective study of 171 COVID-19-positive pediatric patients in ref. 10 Lu et al. [3] reported by the same hospital with the periods of recruitment overlapped. Including duplicates may introduce bias into a systematic review and may affect understanding of the disease and its epidemiology [4]. Thus, we suggest the authors should exclude isolated case reports and repeat case series from the same region or hospital to avoid duplicate data from large retrospective studies.