Characterizing Long COVID Symptoms During Early Childhood

Importance: Recent studies have identified characteristic symptom patterns of long COVID (LC) in adults and children older than 5 years. However, LC remains poorly characterized in early childhood. This knowledge gap limits efforts to identify, care for, and prevent LC in this vulnerable population. Objectives: To identify symptoms that had the greatest difference in frequency comparing children with a history of SARS-CoV-2 infection to those without, to identify differences in the types of symptoms by age group (infants/toddlers [0-2 years] vs preschool-aged children [3-5 years]), and to derive an index that can be used in research studies to identify young children with LC. Design, Setting, and Participants: This was a multisite longitudinal cohort study with enrollment from over 30 US health care and community settings, including infants, toddlers, and preschool-aged children with and without SARS-CoV-2 infection history. Study data were analyzed from May to December 2024. Exposure: SARS-CoV-2 infection. Main Outcomes and Measures: LC and 41 symptoms among infants/toddlers and 75 symptoms among preschool-aged children. Results: The study included 472 infants/toddlers (mean [SD] age, 12 [9] months; 278 infected with SARS-CoV-2; 194 uninfected; 234 male [50%]; 73 Black or African American [16%]; 198 Hispanic, Latino, or Spanish [43%]; 242 White [52%]) and 539 preschool-aged children (mean [SD] age, 48 [10] months; 399 infected with SARS-CoV-2; 140 uninfected; 277 female [51%]; 70 Black or African American [13%]; 210 Hispanic, Latino, or Spanish [39%]; 287 White [54%]). The median (IQR) time between first infections and completion of symptom surveys was 318 (198-494) days for infants/toddlers and 520 (330-844) days for preschool-aged children. A research index was derived for each age group based on symptoms most associated with infection history. The index is calculated by summing scores assigned to each prolonged symptom that was present, where higher scores indicate greater magnitude of association with history of SARS-CoV-2 infection: poor appetite (5 points), trouble sleeping (3.5 points), wet cough (3.5 points), dry cough (3 points), and stuffy nose (0.5 points) for infants/toddlers, and daytime tiredness/sleepiness/low energy (6.5 points) and dry cough (3 points) for preschool-aged children. Among infants/toddlers with infection, 40 of 278 (14%) were classified as having probable LC by having an index of at least 4 points. Among preschool-aged children, 61 of 399 (15%) were classified as having probable LC by having an index of at least 3 points. Participants with higher indices often had poorer overall health, lower quality of life, and perceived delays in developmental milestones. Conclusions and Relevance: This cohort study identified symptom patterns and derived research indices that were distinct between the 2 age groups and differed from those previously identified in older ages, demonstrating the need to characterize LC separately across age ranges.