# Fatigue in children and young people up to 24 months after infection with SARS-CoV-2

## TL;DR

This study tracks fatigue in children and young people up to two years after SARS-CoV-2 infection, finding that fatigue often persists and varies by subgroup.

## Contribution

The study provides longitudinal data on fatigue trajectories in CYP with SARS-CoV-2 infection and validates a single-item fatigue assessment tool.

## Key findings

- Persistent fatigue was observed in 61.6% of participants at least once during 24 months post-infection.
- Fatigue increased over time on average, with faster increases in females and those not meeting Post-COVID Condition criteria.
- A single-item fatigue question showed good sensitivity and specificity for identifying significant fatigue.

## Abstract

Persistent fatigue is common following acute SARS-CoV-2 infection. Little is known about post-infection fatigue trajectories in children and young people (CYP). This paper reports on a longitudinal analysis of the Children and Young People with Long COVID study. SARS-CoV-2-positive participants, aged 11-to-17-years at enrolment, responding to follow-ups at 3-, 6-, 12-, and 24-months post-infection were included. Fatigue was assessed via the Chalder Fatigue Scale (CFQ; score range: 0-11, with ≥4 indicating clinical case-ness) and by a single-item (no, mild, severe fatigue). Fatigue was described cross-sectionally and examined longitudinally using linear mixed-effects models. Among 943 SARS-CoV-2-positive participants, 581 (61.6%) met CFQ case-ness at least once during follow-up. A higher proportion of ever-cases (vs. never-cases) were female (77.1% vs. 54.4%), older (mean age 15.0 vs. 13.9 years), and met Post-COVID Condition criteria 3-months post-infection (35.6% vs. 7.2%). The proportion of CFQ cases increased from 35.0% at 3-months to 40.2% at 24-months post-infection; 15.9% meet case-ness at all follow-ups. Single-item mild/severe responses showed sensitivity (≥0.728) and specificity (≥0.755) for CFQ case ascertainment. On average, CFQ scores increased by 0.448 points (95% CI, 0.252 to 0.645) over 24-months, but there were subgroup differences (e.g., fatigue increased faster in females than males and improved slightly in those meeting Post-COVID Condition criteria 3-months post-infection while worsening in those not meeting criteria). Persistent fatigue was prominent in CYP up to 24 months after infection. Subgroup differences in scores and trajectories highlight the need for targeted interventions. Single-item assessment is a practical tool for screening significant severe fatigue.

The online version contains supplementary material available at 10.1038/s41598-025-24868-x.