Measles, mumps and rubella (MMR) vaccination under-recording in primary care in England: a two-stage cluster survey to inform vaccine optimisation

INTRODUCTION: Achieving 95% coverage for measles, mumps and rubella (MMR) is essential to controlling measles and achieving elimination status. Accurate coverage information is required to identify susceptible populations and inform public health action. This study aimed to estimate the extent of under-recording of MMR vaccinations in digitised primary care records, to inform vaccination optimisation activities. METHODS: We conducted a two-stage cluster survey of patients registered at GP practices, stratified by London and the rest of England, to determine MMR vaccination status and record type (electronically extractable or other) for all patients aged 1-29 years by age group. Firstly, practices extracted MMR vaccination information by electronic query of digital records for eligible patients, with data coded as unvaccinated, partially vaccinated, or fully vaccinated. Secondly, each practice updated the vaccination status for a random sample of 30 partially or unvaccinated patients (five in each age group) by manually searching all available practice records for any vaccinations given but not identified electronically. RESULTS: The GP practice response rate was 48% (279/576). MMR vaccinations were not consistently coded in primary care: among 2-to 4-year-olds with completed MMR vaccination in their primary care record (in any form), 18.3% in England and 11.4% in London appeared partially or unvaccinated by electronic query. This increased to 31.9% (England) and 23.5% (London) among 5- to 9-year-olds, and 31.1% (England) and 24.3% (London) among 10- to 16-year-olds. For all age groups other than 25-29 years, the proportion of patients with incomplete MMR vaccination was slightly higher in London than the rest of England. CONCLUSION: We identified inconsistent coding of MMR vaccinations in primary care records, which is likely to have contributed to underestimation of national coverage over time. However, immunisation gaps persisted even after accounting for inaccurate coding. Recording and coding should continue to be improved, together with addressing barriers to vaccination uptake.