[1] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, Keppel St, London WC1E 7HT, England
[2] Inst Trop Med, Dept Publ Hlth, Antwerp, Belgium
[3] Univ Geneva, Inst Global Hlth, Geneva, Switzerland
[4] Google LLC, Mountain View, CA USA
[5] Univ Lagos, Dept Obstet & Gynaecol, Coll Med, Lagos, Nigeria