Dr Old is a public health physician and is currently the Deputy Director-General and Head of the Public Health Agency, within the New Zealand Ministry of Health.  Prior to his appointment in July 2022 he held joint positions as Associate Chief Medical Officer for Waitematā District Health Board (DHB), and as Clinical Director, Health Gain for Auckland and Waitematā DHBs.  From January 2020 to July 2022 he was seconded to the COVID-19 response for the Northern Region of New Zealand, mostly recently as Chief Clinical Officer since February 2022.  He has previously held executive roles in strategy, community participation, patient experience, and quality improvement.

Dr Old was a 2018/19 Commonwealth Fund Harkness Fellow and was based between the Clinical Excellence Research Center at Stanford University, and the Social Interventions Research Evaluation Network at UC San Francisco where he researched organisational attributes of primary care practices that achieved good outcomes for traditionally underserved populations.

Dr Old received his medical and public health degrees from the University of Auckland and is a Fellow of both the Australasian Faculty of Public Health Medicine and of the New Zealand College of Public Health Medicine.

He was awarded Fellowship of the New Zealand Medical Association in 2011 for services to the profession and the public.