Julie Leask AO is a social scientist and professor in the School of Public Health, Faculty of Medicine and Health, University of Sydney, where she co-leads the Social and Behavioural Insights in immunisation research group. She has qualifications in public health, nursing and midwifery. Her research focuses on the drivers of vaccine uptake, risk communication, and strengthening programs and policy. She is a member of the University of Sydney Institute for Infectious Diseases and a visiting professorial fellow at the National Centre for Immunisation Research and Surveillance. Her previous roles include chair of the WHO Behavioural and Social Drivers (BeSD) of Vaccination working group; WHO Immunisation and Vaccines related Implementation Research advisory committee; and WHO South East Asia Regional Immunisation Technical Advisory Group. She co-founded the Australian Collaboration on Social Science in and the original Vaccine Acceptance Research Network. She was named overall winner of the Australian Financial Review 100 Women of Influence Awards in 2019 and appointed Officer of the Order of Australia in 2024.