Immune profile of T-lymphocytes in pediatric patients recovered of COVID-19: A longitudinal report

A recent report emphasized the burden of severe COVID-19 in immunosuppressed adults during the Omicron wave(1).Pediatric COVID-19 is usually mild, with rare patients developing severe disease, including multisystem inflammatory syndrome(MIS-C)(2).Children and young people(CYP) with comorbidities are at increased risk of unfavorable outcomes(3).The immune profile of the convalescence phase was studied in adults in different periods of time after acute COVID-19(4), but to date, few studies have evaluated the recovery of the immune system in CYP, especially in immunosuppressed patients(5-7).Therefore, the objective of our longitudinal study was to characterize the immune profile of T-lymphocytes in convalescent CYP and compare it to that of non-infected controls in two periods of time: up to 8-months (V1) and after 1-year (V2) of acute COVID-19.This study is a prospective cohort designed to follow patients up to 18-years-of-age who had COVID-19 between 2020-2021, approved by the Institutional Ethics Committee (number:4.835.548).Written consent was obtained from all parents and patients over nine years.COVID-19 convalescent patients were recruited if they had a visit to the emergency department, were hospitalized, or had a routine consultation at Instituto da Criana e do Adolescente, HC-FMUSP, a pediatric tertiary-care hospital in So Paulo, Brazil.Exclusion criteria were not completing two study visits, developing another COVID-19 episode during the study period or receiving a COVID-19 vaccine.For the control group, we recruited CYP without evidence of COVID-19 (no reports of COVID-19 in patients or household members, negative RT-PCR and serology) and without COVID-19 vaccination.The subjects in the control group were matched for age, sex and comorbidities with COVID-19 patients and had only one visit.We collected demographic data and classified the severity of the COVID-19.We performed laboratory exams and collected additional blood samples in EDTA-coated tubes for flow cytometry.The laboratory methods have been previously described(7).