Jocelyn Chan is a medical doctor and PhD Candidate at the University of Melbourne. Her current work addresses one of the leading causes of childhood mortality worldwide – pneumonia. She is overseeing a multi-site study to determine what proportion of children need to receive the pneumococcal conjugate vaccine in order to interrupt disease transmission, a phenomenon known as ‘herd immunity’. The work engages with the complexities of adapting health interventions and disease surveillance to low- and middle-income countries. Jocelyn has a long-standing interest in global public health. Prior to commencing her PhD, she completed field epidemiology training at the Australian National University. She has worked as an epidemiologist with Medecins Sans Frontieres in South Sudan and assisted in the Ebola outbreak response in Sierra Leone with the World Health Organization. She is interested in the use of epidemiology and statistics to provide the evidence to guide effective implementation of health interventions in low-resource settings.