title: Operational challenges in large clinical trials: examples and lessons learned from the gambia pneumococcal vaccine trial.
authors.affiliation: Medical Research Council Laboratories, the Gambia. cuttsf@who.int
authors.forename: Felicity T
authors.initials: FT
authors.lastname: Cutts
authors.forename: Godwin
authors.initials: G
authors.lastname: Enwere
authors.forename: Syed M A
authors.initials: SM
authors.lastname: Zaman
authors.forename: Fred G
authors.initials: FG
authors.lastname: Yallop