An assessment of the effectiveness of the measles immunization programme in Lagos, Nigeria

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Abstract
Sera from 224 children (mean age 10·2 months) were tested for the presence of measles haemagglutinating antibodies prior to measles vaccination. Six to eight weeks later, they were re-tested. The sera conversion rate was 53·5%. The geometric mean titre was 60 in the sero-converters. The sero-converters were significantly younger than the non-sero-converters (P<0·02) and their mean age was 9·79 months; the mean age of non-sero-converters was 10·1 months. The proportion of non-sero-converters was higher in those who were at least 12 months old than in younger children. It therefore appeared that the low sero-conversion rate was due to other factors in addition to persistent maternal antibodies because the results were the opposite of what would be expected if only maternal antibodies were responsible. It is postulated that vaccine inactivation due to poor storage is an important cause of non-sero-conversion and a plea is made for an effective ‘cold chain’ from the time of vaccine manufacture to its use in the clinics.