In a recent study published in PLoS ONE, researchers prospectively followed up with children and young people (CYP) diagnosed with post-coronavirus disease 2019 (COVID-19) condition or long COVID to elucidate long COVID symptom profiles over six months.

Study: Long COVID—six months of prospective follow-up of changes in symptom profiles of non-hospitalised children and young people after SARS-CoV-2 testing: A national matched cohort study (The CLoCk) study. Image Credit: Nhemz/Shutterstock
Study: Long COVID—six months of prospective follow-up of changes in symptom profiles of non-hospitalised children and young people after SARS-CoV-2 testing: A national matched cohort study (The CLoCk) study. Image Credit: Nhemz/Shutterstock


Children and young people (CYP) have usually developed asymptomatic or mild infections in comparison to adults. Post-COVID-19 conditions or long COVID has raised international concerns in CYP. However, data on the trajectory and prevalence of long COVID symptomatology among young individuals are limited.

The authors of the present study previously conducted a systematic review, identifying 21 publications on long COVID in CYP, of which follow-up durations were documented in 13 studies. At three months, the most frequently reported COVID-19 symptoms were insomnia, fatigue, headache, and anosmia. The team observed a low prevalence of headache, cough, abdominal pain, and cognitive issues and a high prevalence of fatigue, fever, diarrhea, muscular pain, anosmia, and breathing difficulties.

About the study

In the present study, researchers assessed the natural course of COVID-19 symptoms at three months and six months post-testing, the prevalence and course of symptoms developed three months post-testing, and those documenting symptoms developed six months post-testing.

The study comprised CLoCK study participants, who were 11- to 17-year-old non-hospitalized CYP, and self-documented long COVID symptoms in online questionnaires three months and six months following polymerase chain reaction (PCR)-confirmed COVID-19 between January and March 2021. COVID-19 patients were matched to CYP not infected by SARS-CoV-2, and of similar sex, age, and residential region, with similar testing months using the United Kingdom (UK) health security agency (UKHSA) nationwide COVID-19 testing dataset.

Data were obtained on more than 30,000 children and young people at six months, one year, and two years following PCR tests between September 2020 and March 2021. Individuals who were initially SARS-CoV-2-negative but developed COVID-19 within six months of PCR testing were excluded from the analysis.

The questionnaires included demographic parameters, the international severe acute respiratory and emerging infection consortium (ISARIC) pediatric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection questionnaire, and the mental health of CYP in England surveys. In addition, the questionnaires included the short Warwick Edinburgh mental well-being scale, Chalder fatigue scale, and elements from the strengths and difficulties questionnaire.


In total, 6,804 individuals reported long COVID symptoms at three months. Between 18 June and 16 August 2021, another 292 individuals responded to the three-month questionnaires within 23.0 weeks post-SARS-CoV-2 testing and summing up to 7,096 individuals. However, after excluding CYP who were SARS-CoV-2-infected after the baseline PCR testing, 3,395 (1,658 and 1,737 SARS-COV-2-positive and SARS-COV-2-negative at study initiation, respectively) CYP were considered for the final analysis.

The response rate was 48%. Among the study participants, 287 SARS-CoV-2-negative and 257 SARS-CoV-2-positive children and young people had been administered COVID-19 vaccines between the three- to six-month follow-up period. After three months of SARS-CoV-2-infected reports, 11 out of 21 most frequent symptoms documented by >10.0% of CYP had decreased, followed by a further decline at six months. By three and six months, the prevalence of fever, chills, cough, sore throat, and myalgia of SARS-CoV-2-positive CYP decreased from 10% to 25% at COVID-19 testing to below 3.0%.

Anosmia prevalence also reduced from 21.0% to 5.0% and 4.0% within three and six months, respectively. In addition, the prevalence of tiredness and breathlessness was reduced, albeit at a slower rate. Among SARS-CoV-2-negative CYP, the team observed similar symptom profiles and trends with lower prevalence rates. Of note, regarding breathlessness and tiredness, the overall prevalence at three months and six months was greater than at testing since the symptoms were documented in novel CYP cohorts who did not report those symptoms before. Among the test-positive individuals, 36%, 68%, and 57% had ≥1.0 symptoms at PCR testing at three months and at six months, respectively.

The corresponding percentages for test-negative individuals were 9.0%, 53%, and 35%, respectively. For PCR-positive individuals, the prevalence rates of unusual tiredness at baseline, three months, and six months were 24%, 40%, and 41%, respectively.  The proportion comprised 13% who initially documented tiredness at baseline and 27% who documented ‘new’ tiredness at three months. At six months, ‘tired’ participants comprised 12.0% of those reporting tiredness at study initiation, 19.0% who reported tiredness at three to six months of testing, and 10% who reported tiredness for the first time at six months. Dizziness prevalence remained constant at all time points.


Overall, the study findings showed that among CYP, the prevalence of particular symptoms documented at PCR testing reduced over time. Similar trends were noted among PCR- positives and PCR negatives, and novel symptoms were documented six months post-testing for both groups of CYP, indicating that the symptoms were not likely to be exclusively a particular consequence of COVID-19.

Acknowledging that SARS-CoV-2 reinfections might have been unidentified, novel symptoms developing after six months of infection must not be viewed exclusively as novel post-COVID-19 symptoms. Irrespective of whether the symptoms could be attributed to COVID-19, many CYP experienced undesired symptoms that require further investigation and potential intervention.

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