 The hospital's HIV/GUM Clinical Directorate was established in April 1991, and is today the largest specialist HIV unit in Europe, caring for more than 5,000 HIV patients, and enjoys a worldwide reputation as a centre of excellence in both the care of HIV-positive patients and a wide range of associated clinical research.The St Stephen's Centre is also home to the core laboratory of the International AIDS Vaccine Initiative (IAVI).Radio Chelsea and Westminster is the hospital's own hospital radio station, available for; patients, staff and the local community.