Coronavirus disease 2019 (COVID-19) has caused mild illness in children, until the emergence of the novel hyperinflammatory condition paediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (PIMS-TS). PIMS-TS is thought to be a post-SARS-CoV-2 immune dysregulation with excessive inflammatory cytokine release. We studied 25 hydroxyvitamin D (25OHD) concentrations in children with PIMS-TS, admitted to a tertiary paediatric hospital in the UK, due to its postulated role in cytokine regulation and immune response. Eighteen children (median (range) age 8·9 (0·3-14·6) years, male = 10) met the case definition. The majority were of Black, Asian and Minority Ethnic (BAME) origin (89 %, 16/18). Positive SARS-CoV-2 IgG antibodies were present in 94 % (17/18) and RNA by PCR in 6 % (1/18). Seventy-eight percentage of the cohort were vitamin D deficient (< 30 nmol/l). The mean 25OHD concentration was significantly lower when compared with the population mean from the 2015/16 National Diet and Nutrition Survey (children aged 4–10 years) (24 v. 54 nmol/l (95 % CI −38·6, −19·7); P < 0·001). The paediatric intensive care unit (PICU) group had lower mean 25OHD concentrations compared with the non-PICU group, but this was not statistically significant (19·5 v. 31·9 nmol/l; P = 0·11). The higher susceptibility of BAME children to PIMS-TS and also vitamin D deficiency merits contemplation. Whilst any link between vitamin D deficiency and the severity of COVID-19 and related conditions including PIMS-TS requires further evidence, public health measures to improve vitamin D status of the UK BAME population have been long overdue.

The purpose of this study was to describe the characteristics of patients with bronchiolitis admitted to a paediatric intensive care unit (PICU), and to evaluate a national registry of hospitalizations (Programme de Médicalisation des Systèmes d'Information; PMSI) as a potential source of epidemiological data. Of the 49 French PICUs invited to take part in a retrospective survey of children aged <2 years who were hospitalized during the 2005–2006 epidemic season, 24 agreed to participate. Overall, 467 children were enrolled: 75% were aged <2 months, 76% had positive respiratory syncytial virus (RSV) tests, 34·9% required non-invasive ventilation, 36·6% were mechanically ventilated, and six infants died. The main neonatal characteristics were: prematurity (31·9%), respiratory disease (16·5%), congenital heart disease (6·4%), receiving mechanical ventilation (11·6%), and bronchopulmonary dysplasia at day 28 (3·8%). For bronchiolitis episode, the kappa coefficient between the survey and PMSI data was good only for mechanical ventilation (0·63) and the death rate (0·86).