Symptoms of long COVID in children under 14 years of age in Denmark

In a recently published study in The Lancet Child and Adolescent HealthThe researchers examined the symptoms of long-term coronavirus disease (COVID) in Danish children under the age of 14 infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Study: Long COVID symptoms in SARS-CoV-2 positive children aged 0-14 years and matched controls in Denmark (LongCOVIDKidsDK): a national cross-sectional study. Credit: New Africa/Shutterstock


Children are at increased risk of COVID 2019 (COVID-19) and post-COVID-19 (Long COVID) syndrome due to the lack of approved childhood vaccines, fearful recommendations for pediatric immunizations, low vaccine uptake, and difficulties with social distancing between children . Knowledge of long-COVID in children is crucial to guide the identification and treatment of COVID-19 and long-COVID through the establishment of multidisciplinary long-COVID clinics.

About the study

In the present cross-sectional and nationwide LongCOVIDKidsDK study, researchers investigated long-term COVID symptomatology and its impact on quality of life and absence from school and daycare in SARS-CoV-2 infected children aged <14 years in Denmark.

The study included a 1:4 ratio of SARS-CoV-2 infected Danish children (cases) with diagnoses confirmed by polymerase chain reaction (PCR) between January 1, 2020 and July 12, 2021 (cases). , and age- and sex-matched controls. The cases were identified from the Danish COVID-19 database and the controls were identified from the Danish reporting system.

Proxy reports were obtained through surveys completed by mothers/fathers/guardians of children under the age of 14. They included the Children’s Somatic Symptoms Inventory 24 (CSSI-24) and the Pediatric Quality of Life Inventory (PedsQL) to obtain data on children’s well-being and overall health. In addition, the survey forms included follow-up questions on 23 long COVID symptoms most commonly reported in the January 2021 Long COVID Quick Survey for Children.

Symptoms included chest pain, abdominal pain, fatigue, mood swings, headache, muscle or joint pain, difficulty concentrating and/or remembering, loss of appetite, cough, dizziness, sore throat, skin rashes, fever, nausea, difficulty breathing, palpitations and extreme paleness. Other symptoms such as skin discoloration, photosensitivity, dark circles under the eyes and chapped lips were also included.

Quality of life was assessed for dimensions such as emotional, physical, social, emotional, and school or day-care functioning in the past month. Only participants with a recall period of >2 months were included in the study. The data were analyzed using logistic regression and descriptive statistics. Differences were considered clinically significant if Hedges’ g-scores were > 0.2.

The PubMed database was searched on January 4, 2021 for studies long examining COVID in children, resulting in a paper containing a case description of five children in Sweden. Also, Google Scholar was searched and found a preprint study from Italy with 75 long COVID children with no controls.

In addition, the website mentioned ongoing studies that reported a high prevalence of long-lasting symptoms. Still, the studies were small, did not include the youngest age groups, and lacked control groups and laboratory-confirmed SARS-CoV-2 reports. Few studies reported that the symptoms are also widespread in the control subjects. In addition, most studies used a four-week time limit for a long COVID, while the World Health Organization (WHO) defined a long COVID as eight weeks in October 2021.


A total of 10,997 responses (28.8%) and 33,016 responses (22.4%) were received for cases and controls, respectively, between July 20, 2021 and September 15, 2021. The mean ages of the cases and controls were 10 years and 10.6 years, respectively. Long COVID was present in 31% (n=427) children aged 0 to 3 years, 26.5% (n=1505) children aged 4 to 11 years and 32.5% (n=1077) of children im Ages 12 to 14 available.

The most frequently reported symptoms in the 0 to 3 year age group were skin rashes, mood swings, abdominal pain, loss of appetite and cough. In the 4- to 11-year-old age group, difficulty concentrating, difficulty remembering, skin rashes, and mood swings were most common. In the 12- to 14-year-old age group, mood swings, difficulty concentrating, difficulty remembering, and fatigue were reported most frequently. As the symptoms persisted, the number of children with the symptoms decreased.

Cases were more likely than controls in children under 3 years of age to have >1 symptom lasting more than 2 months [odds ratio (OR) 1.8], for people between four and 11 years (OR 1.2) and for people between 12 and 14 years (OR 1.2). Significant differences were found in the CSSI-24 scores between the children in the case group and the controls; however, the differences were not clinically relevant.

In contrast, differences of clinical relevance in the PedsQL scores for the emotional dimension between cases and controls for children aged four to 11 years (scores were 80 and 75 for cases and controls, respectively) and for children aged 12 to 14 years (scores were 90 and 85 for cases and controls, respectively). Likewise, the PedsQL scores for the social dimension for children aged 12 to 14 years were higher for cases (median scores were 100 and 95 for cases and controls, respectively).

In children aged 13 months to three years, the number of children with ≥ 16 sick days was higher among cases (28.4%) than controls (18.4%). The corresponding proportions of children reporting ≥ 16 days absence from school or daycare were also higher among cases (23.9%) compared to controls (14.1%).

Similar results were observed for children aged four to 11 years (cases vs. controls 7.0% vs. 3.8% for ≥ 16 days of sick leave; and 6.1% vs. 3.3% for ≥ 16 days of school leave – or daycare absence). The corresponding proportions for the 12 to 14 age group were 9.0% vs. 5.2%; and 6.5% versus 5.0%. The results showed that the cases across all age groups reported more sick days and a larger number of days absent from schools or day care centers in the previous year compared to the controls.


Overall, the study results showed that long-term symptoms were more common in SARS-CoV-2 positive children compared to controls under 14 years of age, with better quality of life scores related to social and emotional functioning in older children of age (four to 11 years and 12 to 14 years of age). Years). However, the clinical differences at the population level appeared to be small.

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