[1] KEMRI Wellcome Trust Res Programme, Dept Publ Hlth Res, POB 43640, Nairobi 00100, Kenya
[2] Univ Oxford, Nuffield Dept Med, Oxford OX3 7BN, England
[3] Minist Hlth, Div Maternal Newborn Child & Adolescent Hlth, Nairobi, Kenya
[4] Univ Nairobi, Dept Paediat & Child Hlth, Nairobi 1967600202, Kenya
[5] Univ Amsterdam, Acad Med Ctr, Dept Global Hlth, NL-1100 DE Amsterdam, Netherlands
[6] London Sch Hyg & Trop Med, Dept Med Stat, London WC1E 7HT, England