1 Hardelid P, et al. BMJ Paediatrics Open 2022;6:e001545. doi:10.1136/bmjpo-2022-001545 Open access SARS-CoV-2 tests, confrmed infections and COVID-19-related hospital admissions in children and young people: birth cohort study Pia Hardelid , 1 Graziella Favarato, 1 Linda Wijlaars, 1 Lynda Fenton, 2 Jim McMenamin, 3 Tom Clemens, 4 Chris Dibben, 4 Ai Milojevic, 5 Alison Macfarlane, 6 Jonathon Taylor, 7 Steven Cunningham, 8 Rachael Wood 2,9 To cite: Hardelid P, Favarato G, Wijlaars L, et al. SARS-CoV-2 tests, confrmed infections and COVID-19-related hospital admissions in children and young people: birth cohort study. BMJ Paediatrics Open 2022;6:e001545. doi:10.1136/ bmjpo-2022-001545 ► Additional supplemental material is published online only. To view, please visit the journal online (http://dx.doi.org/ 10.1136/bmjpo-2022-001545). SC and RW are joint last authors. Received 13 May 2022 Accepted 5 August 2022 For numbered affliations see end of article. Correspondence to Dr Pia Hardelid; p.hardelid@ ucl.ac.uk Original research © Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY. Published by BMJ. ABSTRACT Background There have been no population-based studies of SARS-CoV-2 testing, PCR-confrmed infections and COVID-19-related hospital admissions across the full paediatric age range. We examine the epidemiology of SARS-CoV-2 in children and young people (CYP) aged <23 years. Methods We used a birth cohort of all children born in Scotland since 1997, constructed via linkage between vital statistics, hospital records and SARS-CoV-2 surveillance data. We calculated risks of tests and PCR- confrmed infections per 1000 CYP-years between August and December 2020, and COVID-19-related hospital admissions per 100 000 CYP-years between February and December 2020. We used Poisson and Cox proportional hazards regression models to determine risk factors. Results Among the 1 226 855 CYP in the cohort, there were 378 402 tests (a rate of 770.8/1000 CYP- years (95% CI 768.4 to 773.3)), 19 005 PCR-confrmed infections (179.4/1000 CYP-years (176.9 to 182.0)) and 346 admissions (29.4/100 000 CYP-years (26.3 to 32.8)). Infants had the highest COVID-19-related admission rates. The presence of chronic conditions, particularly multiple types of conditions, was strongly associated with COVID- 19-related admissions across all ages. Overall, 49% of admitted CYP had at least one chronic condition recorded. Conclusions Infants and CYP with chronic conditions are at highest risk of admission with COVID-19. Half of admitted CYP had chronic conditions. Studies examining COVID-19 vaccine effectiveness among children with chronic conditions and whether maternal vaccine during pregnancy prevents COVID-19 admissions in infants are urgently needed. BACKGROUND Children are much less likely to experience hospital admission and mortality related to SARS-CoV-2 infection than adults. 1 In Europe in 2020, 1.7% of COVID-19-related hospital admissions were in children <19 years of age. 2 Over the course of the pandemic, our understanding of how SARS-CoV-2 infection affects children has also improved. Children who experience more severe symptoms of SARS-CoV-2 may present with acute infection symptoms such as fever or cough. 3–5 Other children may develop an acute inflammatory syndrome, paediatric inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS- TS; also referred to as multisystem inflamma- tory syndrome related to COVID-19), several weeks after initial infection. 6–8 Children aged <2 years old appear to be over-represented among children admitted to hospital with acute symptoms, whereas children aged 10 years or older account for the largest propor- tion of admitted PIMS-TS cases. 4 9 Among children admitted to hospital with SARS-CoV-2 or PIMS-TS, those with specific chronic respiratory, neurological, gastrointes- tinal or cardiovascular conditions, and partic- ularly children with multiple comorbidities, were at increased risk of paediatric inten- sive care unit (PICU) admission or death. WHAT IS ALREADY KNOWN ON THIS TOPIC ⇒ Children are less likely to suffer severe symptoms of SARS-CoV-2 infection than adults. There are few population-based studies of the epidemiology of SARS-CoV-2 in children not admitted to hospital. WHAT THIS STUDY ADDS ⇒ Using a national birth cohort from Scotland during 2020, we found that children and young people with chronic conditions were more likely to be tested, but secondary school-aged children with chronic condi- tions were less likely to have a confrmed infection. Infants and children/young people with chronic con- ditions were at highest risk of admission. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY ⇒ Studies examining COVID-19 vaccine effectiveness among children with chronic conditions and wheth- er maternal vaccine during pregnancy prevents COVID-19 admissions in infants are urgently needed. on December 29, 2022 by guest. 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