MMR vaccine uptake rates: a data validation study.

As part of our investigation into the decrease in the measles, mumps and rubella (MMR) vaccine uptake rates, we validated MMR vaccination records of all children born between 01/09/1998 and 31/08/1999 in our area (North Cheshire, South Cheshire, and Wirral). A significant number of children had received their MMR vaccine but were not recorded as such by the Child Health Computer System (CHCS). Reported COVER (cover of vaccination evaluated rapidly) data uptake (combined) for North Cheshire, South Cheshire, and Wirral Health Authorities for the period covered by the data validation study was 90.5%, the corrected uptake following the validation was 92.6%, 2.1% higher than the reported coverage. If the coverage data were to continue to form part of the NHS indicators of PCT performance, action by all PCTs to improve accuracy of immunisation data would be highly desirable. Electronic transfer of information from practices to the CHCS and between CHCSs, i.e. across boundaries, could improve data accuracy.