SARS-CoV-2 seroprevalence among children in Latvia: A cross-sectional study.

Coronavirus disease 2019 (COVID-19) is a major global health concern. In contrast to adults, the course of the disease has been observed to be mild or even asymptomatic in children. It is therefore both clinically and epidemiologically important to measure the seroprevalence in children and adolescents to discern the overall morbidity of the disease and to compare these findings with similar data collected globally. We conducted a cross-sectional study between March and July of 2022 at the Children Clinical University Hospital in Riga, Latvia, to evaluate the seroprevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Participants aged 0 to 18 years were enrolled during hospitalization for reasons other than COVID-19. The levels of SARS-CoV-2 spike protein and nucleocapsid antibodies were measured in blood samples. The possibility of transplacental antibody transport was evaluated by directly interviewing the mothers of participants aged 18 months and younger. Various demographic and epidemiological risk factors and their association with seroprevalence were analyzed. Positive SARS-CoV-2 nucleocapsid antibodies were designated the main criterion for seropositivity. Of 200 enrolled children, 173 were found to be seropositive, resulting in an overall seroprevalence of 86.5%. The highest seroprevalence was detected in children and adolescents aged 12 to 18 years. With the progression of the COVID-19 pandemic, the seroprevalence in children has increased significantly. We found that almost 1-third of seropositive children in our study population were unaware of being previously infected with SARS-CoV-2 due to an asymptomatic course of the disease. Our study findings pertaining to high seropositivity among children and adolescents might be beneficial for public authorities to adapt epidemiological strategies and prevention measures. The high seroprevalence rate reported here and in many other populations around the world suggests that COVID-19 will likely become one of the many seasonal viral infections.

Significant age and gender-related variations of main lymphocyte subsets in pediatric patients: Latvian data.

Age and gender-related variability of main lymphocyte subsets (T, B and NK cell absolute counts and percentages from Ly; T4, T8 and DN cell absolute counts and percentages from lymphocytes and from T cells; T4:T8 and T:B ratios) was studied in a large cohort of pediatric patients (2 days - 17 years) at yearly intervals. 4128 6-color TBNK tests performed on BD FACSCanto II flow cytometer were assessed; patients with immune deficiencies and tumors were not included. The study revealed significant age and gender-related changes in all subsets. Absolute counts of T, B, T4 cells dropped from neonates to adolescents, decrease of T8 and NK cells was milder; relative count of T cells increased with age and that of B cells decreased; T4:T8 ratio went down and T:B ratio grew. Total T, T4 cells and T4:T8 ratio were significantly higher in girls, while T8, NK and DN cells - in boys; significantly higher relative and absolute B cell counts in boys appeared in adolescence. We compared our results with reference values for healthy children (Tosato et al., 2015), there was a good concordance, except for DN cells. Advantages of using patient cohort instead of healthy children as reference, possibilities for adjusting age and gender-specific reference ranges and potential international data pooling are discussed. This article is protected by copyright. All rights reserved.