Accuracy of routine data on MMR vaccination coverage and validity of parental recall of vaccination

A study was conducted to re-validate the measles, mumps and rubella (MMR) coverage and measles susceptibility in children resident in Bolton and born between 1991 and 1995; also to examine the accuracy of parental recall of children's MMR vaccination status. Using general practitioner/practice held records, a validation survey was conducted on a random sample of 171 reportedly unvaccinated children. A questionnaire survey was used to assess parental recall. 'Records' to 'recall' agreement was examined. One- and two-dose population coverage according to routine data was 94.6% and 75.2% respectively, with measles susceptibility of 8.1%. Based on the 'records' survey, one- and two-dose population coverage estimates were 97.4% (+2.8%) and 78.9% (+3.7%), with a revised susceptibility estimate of 5.2%, respresenting a 36% reduction in the susceptibility fraction. Routine data may modestly underestimate vaccination coverage and significantly overestimate measles susceptibility. Many parents of MMR unvaccinated children believe that their children have been vaccinated.