Background Children are less likely to be severely affected or symptomatic from Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) compared to adults. Currently, there is limited evidence on direct comparison of the presentation, clinical features, and managements between infants and older children.

Objectives To understand the difference between the impact of COVID-19 on infants (less than 1 year old) and older children (1 year to 16 years old)

Methods A single-centre retrospective cohort study evaluating children with confirmed COVID-19 who were admitted to University Hospitals of Leicester (UHL), United Kingdom between March to June 2020.

Results Between March to June 2020, a total of 17 children had been hospitalised with subsequent positive SARS-CoV-2 RNA PCR, of which 59% were infant (n=10). Older children had significantly higher CRP compared to infants. All older children (7/7) had elevated CRP ranging between 8 mg/L to 403 mg/L. 71.4% (5/7) of them had CRP more than 100 mg/L. Among the infants, 50% (5/10) had normal CRP (CRP <5 mg/L) and 30% (3/10) had no blood tests taken during admission as they were clinically well. Higher proportion of older children with COVID-19 required admission into paediatric intensive care unit (PICU) or high dependency unit (HDU) and had significantly longer hospital stay compared to infant.

Conclusions Between March and June 2020, hospitalised older children in UHL appeared to be more adversely affected by COVID-19 compared to infants. This may correlate with the emergence of Paediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-CoV-2 (PIMS-TS) and increased incidence of Kawasaki-like disease. Previous findings of infants having more severe disease from COVID-19 by Dong et al might be misleading as it predated the emergence of PIMS-TS and Kawasaki-like disease. The intention of this report is to alert the paediatric community that older children are likely to have a more severe disease when admitted with COVID-19. As this disease is a relatively new entity with evolving clinical picture, clinicians should be open-minded and remain vigilant.