30-year trends in admission rates for encephalitis in children in England and effect of improved diagnostics and measles-mumps-rubella vaccination : a population-based observational study

Background: Encephalitis is a serious neurological disorder, yet data on admission rates for all-cause childhood encephalitis in England are lacking. We aimed to estimate admission rates for childhood encephalitis in England over 33 years, to describe trends in admission rates and to observe how these have varied with the introduction of vaccines and improved diagnostics. Methods: A retrospective analysis of hospital admission statistics for encephalitis for individuals aged 0-19 years was conducted using the English national Hospital Inpatient Enquiry (HIPE, 1979 -1985) and Hospital Episode Statistics (HES, 1990 -2011). Annual age-specific and age standardised admission rates in single calendar years and admission rate trends for specified aetiologies in relation to introduction of polymerase chain reaction (PCR) testing and measles-mumps-rubella (MMR) vaccination. Results: There were 16571 encephalitis hospital admissions (average hospital admission rate (AR): 5·97/100,000/year (95%CI 5·06-6·82)). Hospital ARs declined from 1979-1994 (annual percentage change, APC, 3·30%; 2·88%-3·66%; p<0·0001) and increased between 1995 and 2011 (APC=3·30%; 2·75%-3·85%; p