In the summer of 2011, Seth Berkley moved from New York to Geneva as the new chief executive of the Global Alliance for Vaccines and Immunization (GAVI). For over a decade previously, Berkley had run the International AIDS Vaccine Initiative (IAVI), an institution he had founded. This experience confirmed his status as one of the world’s frontline soldiers in the battle against disease. A polymath and explorer in his spare time, Berkley is a public health specialist of some renown. Trained as a clinical epidemiologist with degrees from Brown and Harvard Universities, Berkley previously worked at the Centre for Disease Control and Prevention, Atlanta, the United States. In 2009, Time magazine named him as one of the ‘100 most influential people in the world’. In a lengthy interview, Berkley answered Seminar’s questions on the immunization challenge, and his mandate at GAVI to make our planet a safer, healthier place.