Quarraisha Abdool Karim, Centre for the AIDS Programme of Research in South Africa (CAPRISA); Department of Epidemiology, Columbia University, New York, USA Salim S. Abdool Karim, Centre for the AIDS Programme of Research in South Africa (CAPRISA); Department of Epidemiology, Columbia University, New York, USA Cheryl Baxter, Centre for the AIDS Programme of Research in South Africa (CAPRISA)