Children who miss immunisation: implications for eliminating measlesBMJ 1995; 310 doi: https://doi.org/10.1136/bmj.310.6991.1367 (Published 27 May 1995) Cite this as: BMJ 1995;310:1367
- Meirion R Evans, consultant in communicable disease controla
- Accepted 9 March 1995
The United Kingdom aims to eliminate indigenous measles by the year 2000. National coverage of measles, mumps, and rubella immunisation is currently 92%, and protective efficacy of measles vaccine is around 90-95%.1 2 Even with high immunisation coverage, however, primary vaccine failure will continue to sustain measles transmission in the community.2 Thus a two dose measles immunisation schedule has been used for several years in the United States and is now proposed for the United Kingdom.3 Most (97%) children who fail to respond to a single dose will produce antibody after reimmunisation.4 The most cost effective option is probably to give a second dose at the same time as the existing preschool booster of diphtheria-tetanus and polio.
For this strategy to be successful it is important to know what proportion of children who miss out on measles, mumps, and rubella immunisation are likely to attend for a preschool booster, and how many will miss out on both. I examined data on children in South Glamorgan to answer these questions.
Subjects, methods, and results
I carried out a retrospective cohort study of all children resident in South Glamorgan who had been born in 1989, using immunisation records held on the child health computer. These records are initially generated from birth notifications and are regularly updated. Information on immunisation status is provided by general practitioners and child health clinics. In South Glamorgan the computer record is used to validate doctors' claims for payment for reaching immunisation targets, so the data are accurate and up to date.
I analysed whether children had been immunised against measles, mumps, and rubella by their second birthday and whether they had received the preschool booster. The relation between the two immunisations was analysed by calculating relative risks and 95% confidence intervals.
Information on 6136 children was available; there were 5868 live births in 1989, the discrepancy being due to transfers in and out of the district (table). Uptake of measles, mumps, and rubella immunisation in the birth cohort was 84.7% by the age of 2 years and that of the preschool booster 87.8% by the age of 5. Of the 936 children who had not had measles, mumps, and rubella immunisation, 420 had not received the booster. Overall, 5200 children were immunised against measles, mumps, and rubella, but 332 of them did not receive the booster. Children who had been immunised against measles, mumps, and rubella were almost twice as likely to receive a preschool booster as those who had not (relative risk 1.70, 95% confidence interval 1.60 to 1.80). Given that all children receiving the booster would also receive measles immunisation if it were offered as a preschool booster, 4868 (79.3%) of the birth cohort would receive two measles doses, 848 (13.8%) would get one measles dose, and 420 (6.8%) would get none.
Concerns over the growing number of older children susceptible to measles have prompted the recent nationwide school immunisation campaign.2 Although this short term measure should prevent the predicted epidemic, a change in immunisation strategy will be required to eliminate measles. Uniform coverage of 95% with a 100% effective vaccine will be required to eliminate measles in a stable population.5 My results indicate that at current immunisation coverage, 6.8% of children would remain completely unimmunised with a two dose measles schedule incorporating a preschool booster. Given a primary vaccine failure of 5-10% for both immunisations and no acquired natural immunity before going to school, between 7.7% and 8.8% of children would remain susceptible to measles. At these rates a further primary school measles immunisation campaign might be necessary within the next few years.
National coverage of measles, mumps, and rubella immunisation has risen considerably over the past five years and preschool booster coverage is also improving (in South Glamorgan, from 84.2% in the 1985 birth cohort to 87.8% in the 1989 birth cohort). This means that a higher proportion of children could be protected against measles by a two dose strategy in future birth cohorts. To ensure success, however, greater efforts will have to be concentrated on tracing persistent non-attenders for immunisation and on improving preschool booster coverage.
I thank the Welsh Health Common Services Authority's child support team for providing the immunisation data for South Glamorgan.