About the Authors

Heidi M. Soeters

hsoeters@email.unc.edu

Affiliation Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America

Charles Poole

Affiliation Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America

Monita R. Patel

Affiliation Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America

Annelies Van Rie

Affiliation Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America

Competing Interests

MRP was a summer intern and research assistant at GlaxoSmithKline in 2010-2011. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: HMS AVR CP. Performed the experiments: HMS. Analyzed the data: HMS. Wrote the manuscript: HMS AVR CP MRP. Developed the search strategy, established inclusion criteria, reviewed abstracts: HMS AVR. Abstracted the study data: HMS MRP. Provided expertise in meta-analytic methods: CP.