[1] London Sch Hyg & Trop Med, Dept Infect Dis Epidemiol, London WC1, England
[2] Publ Hlth England, Modelling & Econ Unit, London, England
[3] CHU Quebec, Ctr Rech, SP POS, Quebec City, PQ, Canada
[4] Univ London Imperial Coll Sci Technol & Med, Dept Infect Dis Epidemiol, London, England
[5] Univ Laval, Dept Med Sociale & Prevent, Quebec City, PQ, Canada
[6] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Int Hlth, Baltimore, MD USA
[7] WHO, Initiat Vaccine Res, CH-1211 Geneva 27, Switzerland