1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
2. Division of Infectious Diseases, Departments of Pediatrics and Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
3. Division of Infectious Diseases, Department of Pediatrics, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA.
4. Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.
5. Department of Immunology and Institute of Medical Sciences, University of Toronto, Toronto, Canada.
6. Center for Biostatistics in AIDS Research, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.