1. Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada;
2. Zvitambo Institute for Maternal Child Health Research, Harare, Zimbabwe;
3. Blizard Institute, Queen Mary University of London, London, United Kingdom;
4. Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD;
5. School of Population and Public Health, University of British Columbia, Vancouver, Canada