1 Duke University School of Medicine, Durham, NC, USA.
2 Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
3 University of California at Los Angeles (UCLA), Los Angeles, CA, USA.
4 University of Birmingham, Birmingham, UK.
5 Moderna, Inc., Cambridge, MA, USA.
6 Great Ormond Street Hospital for Children and Institute for Child Health, NIHR Biomedical Research Centre, London, UK. Stephanie.Grunewald@gosh.nhs.uk.