He works on vaccine trials and disease surveillance. His research brings together epidemiological analysis and laboratory testing to identify optimal methods for disease prevention, focusing on pathogens in low- and middle-income countries such as polio, rotavirus and typhoid. He works with a network of collaborators at institutes worldwide, including in the UK, DRC, France, Ghana, India, Malawi, Pakistan and Zambia. Current research topics: Rapid diagnostics for poliovirus surveillance; Epidemiology of polio eradication and endgame strategy; Environmental surveillance; Vaccine clinical trial design; Causes of oral vaccine failure (rotavirus and poliovirus); Human infection challenge for vaccine development; Typhoid epidemiology