Dr Halliday is a clinician scientist with an interest in immune regulation and liver disease. His research work includes exploration of regulatory T cell biology in the human liver and clinical outcomes for patients with immune mediated liver diseases. He runs a joint liver-immunology service in collaboration with the Clinical Immunology service at the Royal Free Hospital, caring for patients with liver involvement from primary immunodeficiency syndromes.  

Recent publications include the description of the natural history and clinical outcomes of patients with Common Variable Immunodeficiency-related Liver Disease and description of the liver pathology observed in this condition.