COVID-19 Alpha Variant (B.1.1.7): Humoral, memory B and T cells in COVID-19 pediatric convalescents

Background: Studies of anti-SARS-CoV-2 humoral and adaptive response in COVID-19 non-vaccinated pediatric convalescents are controversial and further evidence from the pediatric population are needed. Objectives: To elucidate SARS-CoV-2 humoral and memory B- and T-cells responses in pediatric convalescents as compared with the adult. Methods: Blood samples were obtained from 80 non-vaccinated, IgG-positive, COVID-19 convalescents (age 8.0–61.0 years), 4.0 months from onset. Frequency of responders and magnitudes of SARS-COV-2 IgG, memory B-cells (MBC) and IFNg- and IL2-secreting memory T-cells (MTC) in response to immuno-dominant peptide pools in pediatric, young adults and middle-aged adults with onset age 8–18 years (N = 20), 19–39 years (N = 30) and 40–61 years (N = 30), respectively, were analyzed. SARS-CoV-2 IgG were detected by ELISA (Euroimmun, Germany). MBC, IFNg-, IL2- and IFNg+IL2-secreting MTC (IFNg-MTC, IL2-MTC and IFNg+IL2-MTC) were detected using FluoroSpot (Mabtech, Sweden). Results: MBC level was lower in pediatric as compared with the middle-aged adults (median 12.75 interquartile range [IQR] 4.27–33.7 and 32.0 IQR 6.0–124.2, respectively, p =.003). MBC level in young adults was lower than in middle-aged adults (median 18.5 IQR 1.7–43.8 and 32.0 IQR 6.0–124.2, respectively, p =.006). The level of IL2-MTC was lower in the pediatric group as compared with middle aged-adults (median 2.1 IQR 0–16.9 and 28.6 IQR 11–49.6, respectively, p <.03) and in young adults lower than in middle-aged adults (median 1.45 IQR 0–18.6 and 28.6 IQR 11–49.6, respectively, p =.02). In addition, the level of IFNg-MTC was lower in pediatric as compared with young adults (median 4.25 IQR 0.0–15.0 and 20.9 IQR 0–75.2, respectively, p =.05). The level of IgG was comparable between pediatric and both young and middle-aged adult groups (4.82 ± 2.95, 3.70 ± 2.65 and 4.9 ± 2.94, respectively, p >.34). Conclusion: Non-vaccinated COVID-19 pediatric convalescents have lower adaptive immune responses than adults sustaining the recommendation for vaccination of the pediatric population.