^a Fetal Medicine Unit, Department of Obstetrics and Gynaecology, St George’s Hospital, St George’s University of London, London SW17 0QT, UK 

^b Vascular Biology Research Centre, Molecular and Clinical Sciences Research Institute, St George’s University of London, London SW17 0QT, UK 

^c Paediatric Infectious Diseases Research Group and Vaccine Institute, Institute of Infection and Immunity, St George’s University of London, London SW17 0QT, UK 

^d Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden 

^e Department of Neonatology, Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden 

^f The Royal College of Obstetricians and Gynaecologists, London, UK 

^g Department of Women’s Health, University College London Hospitals NHS Foundation Trust, London, UK 

^h Department of Gynecology and Obstetrics, Hospital das Clínicas, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil 

ⁱ Department of Gynecology and Obstetrics, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil 

^j Immunisation and Countermeasures Division, Public Health England, London, UK 

^k British Paediatric Surveillance Unit, Royal College of Paediatrics and Child Health, London, UK