About the Authors

Alison C. Roxby

aroxby@uw.edu

Affiliation Department of Medicine, University of Washington, Seattle, Washington, United States of America

Claire Atkinson

Affiliation Centre for Virology, Department of Infection, School of Biomedical and Life Sciences, University College London, London, United Kingdom

Kristjana Ásbjörnsdóttir

Affiliation Department of Epidemiology, University of Washington, Seattle, Washington, United States of America

Carey Farquhar

Affiliations Department of Medicine, University of Washington, Seattle, Washington, United States of America, Department of Epidemiology, University of Washington, Seattle, Washington, United States of America, Department of Global Health, University of Washington, Seattle, Washington, United States of America

James N. Kiarie

Affiliation Department of Obstetrics and Gynaecology, University of Nairobi, Nairobi, Kenya

Alison L. Drake

Affiliation Department of Global Health, University of Washington, Seattle, Washington, United States of America

Anna Wald

Affiliations Department of Medicine, University of Washington, Seattle, Washington, United States of America, Department of Epidemiology, University of Washington, Seattle, Washington, United States of America, Department of Laboratory Medicine, University of Washington, Seattle, Washington, United States of America, Division of Vaccine and Infectious Disease, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America

Michael Boeckh

Affiliations Department of Medicine, University of Washington, Seattle, Washington, United States of America, Division of Vaccine and Infectious Disease, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America, Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America

Barbra Richardson

Affiliations Department of Global Health, University of Washington, Seattle, Washington, United States of America, Department of Biostatistics, University of Washington, Seattle, Washington, United States of America, Division of Vaccine and Infectious Disease, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America

Vincent Emery

Affiliation Department of Microbial and Cellular Science, University of Surrey, Guildford, United Kingdom

Grace John-Stewart

Affiliations Department of Medicine, University of Washington, Seattle, Washington, United States of America, Department of Epidemiology, University of Washington, Seattle, Washington, United States of America, Department of Global Health, University of Washington, Seattle, Washington, United States of America, Department of Pediatrics, University of Washington, Seattle, Washington, United States of America

Jennifer A. Slyker

Affiliation Department of Global Health, University of Washington, Seattle, Washington, United States of America

Competing Interests

Please note that GlaxoSmithKline donated valacyclovir and matched placebo to the study. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: JAS CF AW MB VE GJS ALD CA KA. Performed the experiments: CA KA JAS MB VE. Analyzed the data: JAS ALD BAR GJS CF. Wrote the paper: AR JAS GJS CF JK AW KA CA VE BR MB ALD. Conducted the clinical trial: AR AD CF JK.