Is the protection afforded measles vaccines the same in children of all age groups?

Abstract

A prospective study was carried out in the City of Gweru in 1988 toexamine the relationship between age and protection afforded measles vaccinees by the measles vaccine. The age group 10 months to nine years accounted for 240 cases or 87 pc of the 276 measles cases reported in 1988. The disease had shifted towards older age groups with children aged 10 to 59 months accounting for 105 cases or 43,7 pc and those aged five to nine years accounting for 135 cases or 56,3 pc of the 240 measles cases reported in the age group 10 months to nine years. In all the sub-age groups of the age group 10 months to nine years i.e. 10 to 23 months, 24 to 35 months, 36 to 47 months etc. the proportion of vaccinated cases was more than that of unvaccinated cases and the incidence rates in the un vaccinated population were all higher than in the vaccinated population. A correlation of age and relative risk (relative risk was calculated for each sub-age group) showed a significant negative trend (correlation coefficient=-0,79; p = 0,012).