Leicester University, University of Leicester, affiliation not provided to SSRN, Imperial College London, Padua University and Hospital, Government of the United Kingdom - Institute of Cancer Research, Fondazione Policlinico Universitario A. Gemelli IRCCS - Department of Woman and Child Health and Public Health, University of Padua - Department of Woman’s and Child’s Health, Imperial College London - Department of Epidemiology and Biostatistics, Mater Dei Hospital, affiliation not provided to SSRN, Erasmus University Rotterdam (EUR) - Department of General Paediatrics, Imperial College London, affiliation not provided to SSRN, Erasmus University Rotterdam (EUR) - Department of General Paediatrics, Hôpital Robert Debré and Imperial College London - Section of Paediatric Infectious Disease