Measles immunity in children: the 1985 national immunisation survey

In April 1985 a national immunisation survey was conducted, in the course of which blood samples were collected from approximately 3000 randomly selected children throughout the country. The study sample comprised approximately 1000 new school entrants, 1000 standard three pupils, and 1000 form four students. The sera were tested for morbilli antibody using an ELISA technique. Twenty-one percent of the five year olds lacked antibody, suggesting that an overall immunisation rate of about 80% is being achieved. Fourteen percent of the 15 year olds lacked antibody, suggesting that this rate of immunisation is partially interfering with the circulation of the wild virus. We conclude that a sizeable pool of susceptible adolescents is accumulating at a time when some wild virus activity still persists, and anticipate a shift in the peak age of measles infection from the 5-9 to the 10-15 age group. This unfortunate side effect of the national immunisation programme could be minimised by improving immunisation uptake in young childhood. Suggestions are made as to how this could be achieved.