He trained for six years as a nephrologist and transplant physician at the Western Infirmary in Glasgow. Subsequently he worked as a Consultant Nephrologist with a special interest in transplantation at the University Hospital of North Staffordshire. During this period he developed an interest in non-adherence in young adult transplant recipients and transition of care from paediatric to adult care. He established a joint transition process with Birmingham Children's Hospital.
In 2002, Dr Harden joined the Oxford Kidney Unit and Transplant Centre and has continued to pursue his interest in transition, having established joint clinics with Great Ormond Street and Evelina Children's Hospitals in London. He is clinical advisor to the National Health Service in the UK on adolescent transition and young adult services in patients with ESRD. He runs a unique community-based young adult transplant service in Oxford.
In addition Paul Harden is interested in malignancy post-transplantation and the impact of targeted immunosuppression reduction. He is Chief Investigator of the RESCUE (UK) trial of immunosuppression modulation for squamous cell skin cancer post-transplantation. He is currently working with a European consortium on development of a trial of cell therapy to allow immunosuppression reduction.