Harvard University - Massachusetts General Hospital, affiliation not provided to SSRN, affiliation not provided to SSRN, Kenya Medical Research Institute (KEMRI), University of California, San Francisco (UCSF) - Department of Obstetrics, Gynecology & Reproductive Sciences, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, University of Washington - Vaccine and Infectious Disease Division, University of Washington - Department of Global Health and Harvard University - Massachusetts General Hospital