Using a Human Challenge Model of Infection to Measure Vaccine Efficacy: A Randomised, Controlled Trial Comparing the Typhoid Vaccines M01ZH09 with Placebo and Ty21a. oleh Thomas C Darton, Claire Jones, Christoph J Blohmke, Claire S Waddington, Liqing Zhou, Anna Peters, Kathryn Haworth, Rebecca Sie, Christopher A Green, Catherine A Jeppesen, Maria Moore, Ben A V Thompson, Tessa John, Robert A Kingsley, Ly-Mee Yu, Merryn Voysey, Zoe Hindle, Stephen Lockhart, Marcelo B Sztein, Gordon Dougan, Brian Angus, Myron M Levine, Andrew J Pollard