Measles is highly contagious: eighty-five per cent of those exposed to the virus go on to develop symptoms, including an itchy rash, diarrhoea, vomiting and an extremely painful cough. For this reason, sufferers are often quarantined. Prior to the introduction of routine immunization in 1963, the disease was a major problem. Large-scale outbreaks occurred on a two- or three-yearly basis, with young children being particularly at risk. Complications were common and could be severe; in a significant number of cases, they were fatal.