Severe acute COVID-19 and early long COVID signals in paediatric cohorts: an analysis of real-world data from two health departments, Germany

Severe acute coronavirus disease 2019 (COVID-19) is uncommon in children; however, its development can lead to longer-term health problems. Understanding factors associated with clinical deterioration in paediatric patients is therefore of public health relevance. Early triage enables closer monitoring, tailored counselling, and timely escalation of care. International studies have associated obesity, chronic illness, and certain sociodemographic factors with worse outcomes. However, robust real-world datasets remain sparse, particularly in Germany, where statutory surveillance often fails to capture detailed clinical data. To address this gap, we analysed 731 polymerase-chain-reaction (PCR)-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in children aged ≤ 15 years reported to the Cologne and Augsburg health departments between January and December 2021. • Primary: Identify independent factors associated with a severe acute COVID-19 course in this population-based study with defined sampling framepaediatric cohort. • Secondary (exploratory): Estimate the prevalence of long COVID–compatible symptoms (persisting >4 weeks) and explore how their frequency changes across acute COVID-19 severity strata. This analysis is based on the CoCo-Fakt cross-sectional study, which captured 731 PCR-confirmed SARS-CoV-2 infections in children aged ≤15 years between January and December 2021. The parent questionnaire captured sociodemographic variables, body mass index (BMI), chronic illnesses, quarantine details, acute COVID-19 severity (asymptomatic to severe), and persisting symptoms (>4 weeks). We then used multivariable logistic regression to examine whether age, sex, socioeconomic status, migration background, BMI, and chronic illness were independently associated with a severe disease course. For exploratory comparisons between children with and without long COVID, we applied t-tests for continuous and Fisher’s exact or chi-square tests for categorical variables. Among the included participants, 67 (9.6%) experienced a severe disease course of COVID-19. In multivariable analysis, chronic illness emerged as the only independent factor associated with severe COVID-19, conferring an almost sixfold higher odds of severe COVID-19 (OR 5.90, 95% CI 2.98–11.68). BMI showed a positive trend but was not statistically significant. Exploratory analyses indicated associations with older age, chronic illness, and increasing acute disease severity. The most frequently reported symptoms were fatigue, sleep disturbances, and problems concentrating. Chronic illness was consistently associated with a higher likelihood of severe acute COVID-19 in children. Given the cross-sectional design, exploratory, parent-reported data suggest older age and more severe acute disease courses may increase the likelihood of persisting symptoms, which warrants confirmation in prospective cohorts. Therefore, children with more severe acute disease or chronic illness may benefit from tailored follow-up to better understand potential long-term impairment, including potential progression to myalgic encephalomyelitis/chronic fatigue syndrome.