The changing age ecology of measles and its implications on measles control.

In the City of Gweru measles vaccination was commenced in 1971. With the advent of the Expanded Programme on Immunisation in 1981-82, measles vaccination coverage was increased, reaching over 80 pc in 1985 and after. Despite this vaccination effort measles morbidity rates have remained high and epidemics continue to occur periodically. It is argued that the shift of the disease from young age groups to older children, coupled with the fact that there are more vaccinees amongst cases with the disease, will mean that transmission will continue uninterrupted. Possible reasons for persistent transmission in older children are explored. It is concluded that measles revaccination is required to interrupt measles transmission.