Biomarkers of long COVID in children and young adults: a scoping review

Following the SARS-CoV-2 pandemic, a significant percentage of people are now experiencing long-term symptoms, despite a continuing lack of concrete documentation of physiological and risk profiles that hinders diagnosis and treatment, particularly in pediatric contexts. This review aims to highlight the existing evidence for measurable physiological markers for post-acute sequelae of SARS-CoV-2 infection (long COVID) in children, adolescents, and young adults. Titles providing data related to measurable biomarkers distinguishing young long COVID patients from controls were compiled and analyzed. Results were displayed in table and diagram form for optimal qualitative evaluation of the relationship between markers and symptomatology within the context of each organ system. Only human studies published in English, Italian, Portuguese, German, and Spanish between the 5th of February 2025 and the 31st of December 2025 were considered, and no other time constraints were applied. Following search and criteria evaluation, nine studies were included, totaling 41 occurrences identified in diseased patients with statistically significant variation from healthy controls. Markers suggest the presence of organic manifestations based on published literature, although more data and future studies will be necessary to establish clear connections.

The data compiled for this review adds to the body of evidence indicating a physiological manifestation of long COVID and its consequences. Further investigation into potential risk factors, pre- and post-pubescent manifestations, and specific inflammatory and immune pathways will be necessary for a more concrete understanding of long COVID and its effects on children, adolescents, and young adults.

• Long COVID is estimated to affect a significant population of patients, despite the lack of concrete physiological diagnostic and prognostic measures. • Pediatric incidence of the disease is still largely debated, and published data are scarce.

• A total of 41 biomarker occurrences were identified by selected studies, which were consistent with expected physiology behind reported symptoms. • The body of data discussed suggests the presence of physiological phenomena behind the long-term symptoms experienced by pediatric long- COVID patients.