key: cord-0900570-32ut5vr7
authors: Osmanov, Ismail M; Spiridonova, Ekaterina; Bobkova, Polina; Gamirova, Aysylu; Shikhaleva, Anastasia; Andreeva, Margarita; Blyuss, Oleg; El-Taravi, Yasmin; DunnGalvin, Audrey; Comberiati, Pasquale; Peroni, Diego G; Apfelbacher, Christian; Genuneit, Jon; Mazankova, Lyudmila; Miroshina, Alexandra; Chistyakova, Evgeniya; Samitova, Elmira; Borzakova, Svetlana; Bondarenko, Elena; Korsunskiy, Anatoliy A; Konova, Irina; Hanson, Sarah Wulf; Carson, Gail; Sigfrid, Louise; Scott, Janet T; Greenhawt, Matthew; Whittaker, Elizabeth A; Garralda, Elena; Swann, Olivia; Buonsenso, Danilo; Nicholls, Dasha E; Simpson, Frances; Jones, Christina; Semple, Malcolm G; Warner, John O; Vos, Theo; Olliaro, Piero; Munblit, Daniel
title: Risk factors for long covid in previously hospitalised children using the ISARIC Global follow-up protocol: A prospective cohort study
date: 2021-07-01
journal: Eur Respir J
DOI: 10.1183/13993003.01341-2021
sha: ab59ba73015ffec737866e3e6ddb597e9afcd55c
doc_id: 900570
cord_uid: 32ut5vr7

BACKGROUND: The long-term sequelae of coronavirus disease 2019 (Covid-19) in children remain poorly characterised. This study aimed to assess long-term outcomes in children previously hospitalised with Covid-19 and associated risk factors. METHODS: This is a prospective cohort study of children (≤18 years old) admitted with confirmed Covid-19. Children admitted to the hospital between April 2, 2020 and August 26, 2020, were included. Telephone interview using the International Severe Acute Respiratory and emerging Infection Consortium (ISARIC) Covid-19 Health and Wellbeing paediatric follow-up survey. Persistent symptoms (>5 months) were further categorised by system(s) involved. FINDINGS: 518 of 853 (61%) of eligible children were available for the follow-up assessment and included in the study. Median age was 10.4 years (IQR, 3–15.2) and 270 (52.1%) were girls; median follow-up since hospital discharge was 256 (223–271) days. At the time of the follow-up interview 126 (24.3%) participants reported persistent symptoms among which fatigue (53, 10.7%), sleep disturbance (36, 6.9%,) and sensory problems (29, 5.6%) were the most common. Multiple symptoms were experienced by 44 (8.4%) participants. Risk factors for persistent symptoms were: older age “6–11 years” (odds ratio 2.74 (95% confidence interval 1.37 to 5.75) and “12–18 years” (2.68, 1.41 to 5.4); and a history of allergic diseases (1.67, 1.04 to 2.67). INTERPRETATION: A quarter of children experienced persistent symptoms months after hospitalization with acute covid-19 infection, with almost one in ten experiencing multi-system involvement. Older age and allergic diseases were associated with higher risk of persistent symptoms at follow-up.

Emerging data suggest that a substantial proportion of people experience ongoing symptoms including fatigue and muscle weakness, breathlessness, and neurological problems more than 6 months after the acute phase of Covid-19 [1, 2] . This phenomenon is commonly referred to as 'long Covid', a term defined by patient groups, and also known as post-Covid syndrome, the post-Covid-19 condition [3] or 'Covid long-haulers [4, 5] . Recent population data from the UK reported that the highest prevalence of long Covid after 12 weeks was among those aged 25 to 34 years (18.2%) and lowest in the 2 to 11 years age bracket (7.4%) [6] .

Evidence on post-acute covid condition and long term outcomes in children is still limited to small studies with more than half having at least one persisting symptom 4 months after covid-19 infection [7] . However, a recent publication from Australia suggested that only 8% of children aged 0-19 years (median 3 years) had ongoing symptoms 3-6 months after predominantly mild covid-19 infection. The limitation of the study as acknowledged by the authors was the low age range. This mandates the larger numbers inclusion particularly of older children in future studies [8] .

There is a need to assess the long-term consequences of Covid-19 in paediatric populations [9] , to inform clinicians, researchers and public health experts and address the impacts of this condition on those affected and their families and to inform discussions on vaccination of children. This cohort study aimed to investigate the incidence of and risk factors for long- 

This is a prospective cohort study of children (≤18 years old) admitted with suspected or The acute-phase dataset included demographics, symptoms, co-morbidities, chest computer tomography (CT), supportive care, and clinical outcomes at discharge. This study was approved by the Moscow City Independent Ethics Committee (abbreviate 1, protocol number 74). Parental consent was sought during hospital admission and consent for the follow-up interview was sought via verbal confirmation during telephone interview.

Interviews were undertaken by a team of medical students with experience gained in previous Covid-19 research [2, 11] who underwent standardised training in telephone assessment, REDCap data entry and data security. Assessments were conducted via interviews with the parents/carers. Non-responders were contacted by telephone three times before considering them lost to follow-up. Information about the current condition and persisting symptoms was collected using the version 1.0 of the ISARIC COVID-19 Health and Wellbeing Follow-Up Survey for Children, to assess patients' physical and psychosocial wellbeing and behaviour, with local adaptations (addition of questions related to signs/symptoms presence which symptom duration), translated into Russian. The protocol was registered at The Open Science Framework [12] . The follow-up survey documented data on demographics, parental perception of changes in their child's emotional and behavioural status (including reasons for a change covid-19, pandemic or both), previous vaccination history, hospital stay and readmissions, mortality (after the initial index event), history of newly developed symptoms between discharge and the follow-up assessment, including symptom onset and duration, and overall health condition compared to prior to the child's Covid-19 onset (Supplementary file). To assess the prevalence of symptoms over time parents were asked the following: (a) Within the last seven days, has your child had any of these symptoms, which were NOT present prior to their Covid-19 illness? (If yes, please indicate below and the duration of the symptom/s) and (b) Please report any symptoms that have been bothering your child since discharge that are not present today. Please specify the time of onset and duration of these symptoms.

REDCap electronic data capture tools (Vanderbilt University, Nashville, TN, USA) hosted at Sechenov University and Microsoft Excel (Microsoft Corp, Redmond, WA, USA) were used for data collection, storage and management [13, 14] . The baseline characteristics, including demographics, symptoms on admission and comorbidities were extracted from EMRs and entered into REDCap.

For the purposes of this study, we defined "persistent symptoms" as symptoms present at the time of the follow-up interview and lasting for over 5 months. These were subcategorised into respiratory, neurological, sensory, sleep, gastrointestinal, dermatological, cardiovascular, fatigue and musculoskeletal (Table S1) informed by previously published literature [15, 16] and ISARIC Global Paediatric Covid-19 follow-up working group discussions.

Allergic diseases were defined as a presence of any of the following: asthma, allergic rhinitis, eczema or food allergy. Participants age categories were based on Eunice Kennedy Shriver National Institute of Child Health and Human Development Pediatric Terminology [17] .

Severe disease was defined as having received non-invasive ventilation, invasive ventilation or admission to the paediatric intensive care unit (PICU) during the hospital admission.

Health status before Covid-19 and at the time of the interview was assessed using a 0 to 100 wellness scale [18] , where 0 was the worst possible health and 100 the best possible health.

Descriptive statistics were calculated for baseline characteristics. Continuous variables were summarised as median (with interquartile range) and categorical variables as frequency (percentage). The chi-squared test or Fisher's exact test was used for testing hypotheses on differences in proportions between groups. The Wilcoxon rank-sum test was used for testing the hypotheses on differences between groups.

We performed multivariable logistic regression to investigate associations of demographic characteristics, co-morbidities (limited to those reported in ≥5% of participants), presence of pneumonia during acute infection and severity of Covid-19 with persistent symptom categories presence at the time of the follow-up interview. We included all participants for whom the variables of interest were available in the final analysis, without imputing missing data. The differing denominators used indicate missing data. Odds ratios were calculated together with 95% confidence intervals (CIs).

Upset plots were used to present the coexistence of persistent symptom categories. Twosided p-values were reported for all statistical tests, a p-value below 0.05 was considered to be statistically significant. Statistical analysis was performed using R version 3.5.1. Packages used included dplyr, lubridate, ggplots2, plotrix and UpSetR.

The survey was developed by the ISARIC Global Paediatric Covid-19 follow-up working group and informed by a wide range of global stakeholders with expertise in infectious diseases, critical care, paediatrics, epidemiology, allergy-immunology, respiratory medicine, psychiatry, psychology and methodology and patient representatives. The survey was distributed to the members of the patient group and suggestions from parents/carers were implemented.

All 853 children hospitalised with suspected Сovid-19 to the hospital between April 2, 2020 and August 26, 2020 were discharged alive (Figure 1 ). Of 836 patients with accurate contact information, parents of 518 RT-PCR positive children agreed to be interviewed (response rate 62%) and were included in the analysis.

The median age was 10.4 years (IQR, 3-15.2; range, 2 days-18 years), 272 (52.2%) were girls.

Median follow-up time since hospital admission was 268 days (IQR 233-284). Children had a median of 8 (IQR, 4-9) years of formal school education and a median of 4 (IQR, [3] [4] [5] family members were residing in the household ( Table 1) .

The most common pre-existing comorbidity in this cohort was food allergy (13%, 67/514), followed by allergic rhinitis and asthma (9.7%, 50/514), gastrointestinal problems ( Table S4 .

The prevalence of the symptoms present at the time of discharge declined over time ( Figure   2 ). Number of children with fatigue fell from 15.8% (82/518) at the time of discharge to 8.8%

(45/513) 6-7 months later, altered sense of smell from 8.7% (45/518) to 4.7% (24/514), sleep disturbance 7.5% (39/518) to 5.8% (30/515), altered sense of taste from 5.6% (29/518) to 3.1% (16/515), headache from 4.6% (24/518) to 3.5% (18/517), and breathing difficulties from 3.9% (20/518) to 1% (5/517), respectively. The prevalence of the most common symptoms including symptoms that developed some time after discharge are shown in Figure S1 .

With regard to persistent symptom categories ( A total of 8.5% (44) participants reported persistent symptoms from more than one category at the time of the follow-up assessment. Most commonly co-occurring categories were fatigue and sleep problems in 1.9% (10) of children, and fatigue and sensory problems were present in 1.5% (8) of participants. 2.7% (14) of children had persistent symptoms from three or more different categories. Co-existence of persistent symptom categories at the time of the follow-up is presented in the upset plot (Figure 3 ).

The scores on the wellness scale for children with one or two or more persistent symptoms significantly declined when compared to before Covid-19 onset from 90 (80-100) to 82.5 (70-93.8) and from 90 (80-95) to 70 (60-80) (p<0.001 for all comparisons), respectively.

Children who did not experience any persistent symptoms did not report any significant changes in wellness when asked to compare to how they felt before their acute Covid-19 illness. We also assessed emotional difficulties, social relationships, and activity levels in children (Tables S4 -S5) . Parents related the following changes to Covid-19 illness, and not to the pandemic in general: less eating in 4.5% (23/512) of children, less sleeping in 3.5% (18/511) and more sleeping in 2% (10/511), reduced physical activity in 4.7% (24/512) and child becoming less emotional in 4.3% (22/511). In contrast, parents attributed changes to social activities to the pandemic in general rather than to the Covid-19 illness: 12% (58/485) of children were spending less time with their friends in person, while 13% (61/470) were spending more time with friends remotely, with less than one percent of parents attributing these changes to Covid-19 illness. 23% (110/478) of children were spending more time watching television, playing video/computer games or using social media for educational purposes, with 92.9% of parents associating these changes with the pandemic in general rather than the Covid-19 illness.

In multivariable regression analysis, older age group was associated with persistent symptoms (Figure 4) . When compared with children under two years of ages, those ages 6-11 years had an odds ratio of 2.74 (95% confidence interval 1.37 to 5.75) of persistent symptoms and those 12-18 years of age (OR 2.68, 95% CI 1.41 to 5.4) both vs. <2 years.

Another predictor associated with persistent symptoms was allergic diseases (OR 1.67, 95% CI 1.04 to 2.67). Similar patterns were seen for children with co-existence of persistent symptoms from 2 or more categories: 6-11 years of age (OR 2.49, 95% CI 1.02 to 6.72), 12-18 years of age (OR 3.18, 95% CI 1.43 to 8.11) both vs. <2 years.

We ran an additional regression analyses, using "age" as a continuous variable ( Figure S2) which brought similar result. When subgroup analyses were performed in the age group of six years and above, severe acute Covid-19 was associated with persistent symptoms (OR 6.14, 95% CI 1.27 to 43.94) and excessive weight and obesity with co-existence of persistent symptoms from 2 or more categories (OR 2.89, 95% CI 1.12 to 7.15) ( Figure S3 ).

To our knowledge, this is the largest prospective paediatric cohort study with the longest follow-up, assessing symptom prevalence and duration of long COVID in children and adolescents with laboratory confirmed SARS-CoV-2 infection post hospital discharge. We found that a quarter of children and adolescents had persistent symptoms at the time of the follow-up with fatigue, sleep disturbance and sensory problems being the most common.

Almost one in ten reported multi-system impacts with two or more categories of persistent symptoms at the time of the follow-up. Children in mid-childhood and adolescence (age [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] were at higher risk of persistent symptoms at the time of the follow-up. Although prevalence of symptoms declined over time, a substantial proportion experienced problems many months after discharge.

Although many children experienced symptoms, such as fatigue, disturbed smell and taste, sleep and respiratory problems, hair loss and headaches at the time of the hospital discharge, we witnessed a steady decline in the symptom prevalence over time. This was particularly evident for fatigue and smell disturbance. Prevalence of some symptoms such as headache, and sleep problems declined slower, which may be driven by psychological mechanisms rather than pathophysiologic virus infection effects [19] . A limitation of these findings is that symptom onset and duration was recalled at the single follow-up interview in our study; this may be overcome with repeated follow-ups at appropriate intervals to limit potential recall imprecision. There are very few studies assessing long COVID in children and adolescents; a previous smaller study from Italy found similar persisting symptoms during a shorter followup [20] . In line with our results, previous research demonstrated symptoms fading over time in adults [15] but data are still limited as most of the published cohort studies do not measure symptom duration, but rather assess their presence at a single follow-up.

We found that almost one in ten children had multisystem impacts with two or more categories of persistent symptoms present at the time of the follow-up. Similar numbers were previously reported in the Russian adult population [2] and patients with clusters of different symptoms were described in the UK [21] . Patients with multisystem involvement will represent the primary target for the future research and intervention strategies development.

Age was significantly associated with persistent symptom presence at the time of the followup, with children above 6 years of age being at higher risk. To our knowledge, risk factors for long Covid in children have not been investigated in previous studies, so we may draw comparisons with the data from adult cohorts only. Previous data suggest that long Covid is prevalent in adults [1, 2, [21] [22] [23] [24] and that age is associated with a higher risk of long Covid [21, 23] . An Australian follow-up study of 151 children (median 3 years) who had predominantly mild acute covid-19 infection [8] found only 8% with on-going long-covid symptoms. As acknowledged by the authors the low median age may be the main reason for the low long-covid prevalence and our study substantiates this. We also found that in children of six years of age and above, severe acute Covid-19 was associated with persistent symptoms and excessive weight and obesity with multisystem involvement, but confidence intervals were wide and these findings require confirmation on a larger sample size to make any firm conclusions.

We found that allergic diseases in children were also associated with a higher risk of long Covid. This is in agreement with adult studies from Russia [2] and the UK [21] reporting asthma to be associated with development of long Covid. Recent data suggested that COVID-19 consequences may be linked with the mast cell activation syndrome [25] and the Th-2 biased immunological response in children with allergic diseases may be responsible for an increased risk of long-term consequences from the infection. This highlights importance of further research of potential underlying immunological and autoimmune mechanisms of long Covid [26] .

Apart from physical symptoms we assessed emotional and behavioural changes. Although most parents reported no changes, one in twenty parents noticed changes in their children, which they attributed to Covid-19 illness rather than the general situation during the pandemic. These included changes in eating, sleeping, emotional wellbeing and physical activities. Over one in ten parents noted that their children were spending less time in faceto-face communication and more time interacting with their friends remotely and spending time online for both educational and non-educational purposes. These changes were largely attributed to the general situation during the pandemic rather than to the Covid-19 illness.

The "lockdown" measures were implemented in Moscow in the middle of March and lasted until June 2020. Restrictions included self-isolation, public places closures, including schools/universities social distancing, etc. Pandemic resulted in increased anxiety levels among population, which was associated with increased media consumption [27] . The effect of pandemic, illness or both should be further studied in the future research.

A major strength of this study is that it was based on the ISARIC COVID-19 Health and Wellbeing Follow-Up Survey for Children which will assist with data harmonisation and comparison with other international studies in the future. Another strength is the large sample size of confirmed Covid-19 infected children, and this cohort has the longest followup assessment of hospitalised children to date. Stratification to determine if the symptoms were persistent following Covid-19 and assessment of trends over time were other novel aspects of the study. At the same time, this cohort study has several limitations. First, the study population only included patients within Moscow, although regional clustering is common to many cohort studies published during the Covid-19 pandemic. Second, it included only hospitalised children, not representative of paediatric population. Third, we did not have a control group of previously hospitalised children not experiencing Covid-19 infection. Fourth, some patients may have developed additional comorbidities or complications since the hospital discharge, which were not appropriately captured and could potentially affect the wellbeing and symptom prevalence and persistence. Fifth, the parents/caregivers were interviewed in this study and not children themselves. There is also a risk of selection bias due to recruitment of the hospitalised population and recall bias in reporting symptoms which were non-existent at the time of the follow-up and potential selection bias with those with symptoms more likely to agree to survey.

The study used to generate this data within the ISARIC WHO Clinical Characterisation Protocol initiative is a prospective pandemic preparedness protocol which is agnostic to disease and has a pragmatic design to allow recruitment during pandemic conditions. The reality of conducting research in outbreak conditions do not allow for appropriate coenrolment of a control group, which is not practical. One of the issues which has not been addressed so far in clinical research is what control group of individuals admitted to hospital during this period when hospitals were overwhelmed with Covid-19 cases could provide a valid control group. The design of this study allows only to describe the feature of Covid-19 survivors and cannot involve a control group. Сovid-19 is not just a respiratory tract infection so there is no one-fit-all control group. At present, to our knowledge, all major publications on long Covid are uncontrolled cohorts due to the difficulties of ascertaining data among controls matched for age and sex but most importantly matched for the same experiences during the pandemic aside from confirmed Covid-19 illness.

Our findings have implications for further research. Longer follow-up duration and repeated assessments combined with controls and sampling for further studies into the pathophysiology and immunology of post-Covid-19 illness sequelae are needed to inform case definitions, and intervention trials aimed to improve long term outcomes.

Although symptoms which were present at discharge diminished over time, even eight months after hospital discharge many children experienced persistent symptoms, with fatigue, sensory changes and sleep problems being the most common sequelae. One in ten children experienced multi-system involvement at the time of the follow-up. Age and allergic disease were the main risk factors for persistent symptoms. Future work should be multidisciplinary, prospective, preferably with a control cohort, repeated sampling and with an ability for children to report their health and wellbeing themselves, accompanied by biological sample collection to establish causative mechanisms for a better understanding of Covid-19 sequelae and help with the phenotype/endotype categorisation. Odds ratios and 95% CIs for presence of (A) any category of persistent symptoms (n=127) at the time of follow-up and (B) two or more co-existing categories of persistent symptoms (n=73) at the time of the follow-up.

Neurological conditions include "neurological disorders" and/or "neurodisability". Abbreviation: CI, confidence interval. 

To answer the following questions, please mark an X on the lines below that shows your opinion on the question. If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Tingling feeling/ "pins and needles" □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure

If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Seizures/fits □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Confusion/lack of concentration □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Problems speaking or communicating □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Insomnia (hard to fall asleep, hard to stay asleep)

If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Hypersomnia (excessive daytime sleepiness or prolonged nighttime sleep)

If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Fatigue □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure

If yes, what was the time of onset Diarrhea □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Stomach/ abdominal pain □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Feeling nauseous □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Vomiting □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Constipation □ Yes □ No If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Cardiovascular problems Tick Yes or No If yes, what was the time of onset Palpitations (heart racing) □ Yes □ No □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure

If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ Not sure Variations in heart rate (tachycardia or bradycardia)

If yes, what was the time of onset □ < If yes, what was the time of onset □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 -12 months □ >12 months □ From the time of discharge □ Not sure If yes, what was the duration of symptoms □ < 1 month □ 1-2 months □ >2 -3 months □ >3-4 months □ >4-5 months □ >5-6 months □ >6-7 months □ >7 -8 months □ >8-9 months □ >9 -10 months □ >10-11 months □ >11 - 12 

Thank you for your time! The differing denominators used indicate missing data. The differing denominators used indicate missing data. The differing denominators used indicate missing data. Figure S1 . The proportion of COVID-19 infected children who at various time points after discharge from hospital had one or more of the commonest continuing symptoms. Some children had more than one symptom.

The prevalence was calculated based on responses to the following questions: "Within the last seven days, has your child had any of these symptoms, which were NOT present prior to their Covid-19 illness? (If yes, please indicate below and the duration of the symptom/s) and "Please report any symptoms that have been bothering your child since discharge that are not present today.

Please specify the time of onset and duration of these symptoms." Figure S2 . Multivariable logistic regression model to identify pre-existing risk factors for post-COVID condition (using age as a continuous variable). Odds ratios and 95% CIs for presence of (A) any category of persistent symptoms at the time of follow-up and (B) two or more co-existing categories of persistent symptoms at the time of the follow-up. Neurological conditions include "neurological disorders" and/or "neurodisability". Abbreviation: CI, confidence interval. Figure S3 . Multivariable logistic regression model to identify pre-existing risk factors for post-COVID condition (subgroup analyses in children ≥6 years of age). Odds ratios and 95% CIs for presence of (A) any category of persistent symptoms at the time of follow-up and (B) two or more co-existing categories of persistent symptoms at the time of the follow-up. Neurological conditions include "neurological disorders" and/or "neurodisability". Abbreviation: CI, confidence interval.

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We are very grateful to the Z.A. Bashlyaeva Children's Municipal Clinical Hospital clinical staff and to the patients, parents, carers and families for their kindness and understanding during these difficult times of COVID-19 pandemic. We would like to express our very great appreciation to ISARIC Global COVID-19 follow-up working group for the survey development. We would like to thank Mr Maksim Kholopov for providing technical support in data collection and database administration. We are very thankful to Eat & Talk, Luch, Black Market, FLIP and Academia for providing us the workspace in time of need and their support of Covid-19 research. Finally, we would like to extend our gratitude to the Global ISARIC team, the ISARIC global adult and paediatric Covid-19 follow-up working group, and ISARIC Global support centre for their continuous support, expertise and for the development of the outbreak ready standardised protocols for the data collection.

This study did not have external funding.