The high morbidity associated with a measles outbreak in a West Australian town

Objective: To determine the effectiveness of the measles vaccine and to record the morbidity during a measles outbreak. Methodology: A retrospective cohort study was carried out. It was a community-based study in Bunbury, Western Australia, between February and May 1994, of 53 cases of measles and their household contacts. Results: Of the 53 cases of measles, 24 were from one high school. Only two cases occurred in the high school class that had received the National Health and Medical Research Council of Australia recommended measles, mumps and rubella (MMR) booster 12 months earlier. Neither had been vaccinated. Vaccine effectiveness was 91% (95% confidence interval 67-97%). Ten cases had complications of measles and a further five were admitted to hospital. Doctors prescribed antibiotics to 29 cases and metoclopramide to five cases. One month elapsed between the day the index case became ill and the first notification to the community health centre. Conclusions: The low herd immunity that led to this high school outbreak can be attributed to low vaccine coverage. There was a significant morbidity associated with this outbreak that may have been averted if earlier notification had occurred. The MMR booster dose should be offered to all 10-16 year olds to prevent high school outbreaks.