title: 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.
abstract: Encephalitis is a serious neurological disorder, yet data on admission rates for all-cause childhood encephalitis in England are scarce. We aimed to estimate admission rates for childhood encephalitis in England over 33 years (1979-2011), to describe trends in admission rates, and to observe how these rates have varied with the introduction of vaccines and improved diagnostics.
  
  
  
  We did a retrospective analysis of hospital admission statistics for encephalitis for individuals aged 0-19 years using national data from the Hospital Inpatient Enquiry (HIPE, 1979-85) and Hospital Episode Statistics (HES, 1990-2011). We analysed annual age-specific and age-standardised admission rates in single calendar years and admission rate trends for specified aetiologies in relation to introduction of PCR testing and measles-mumps-rubella (MMR) vaccination. We compared admission rates between the two International Classification of Diseases (ICD) periods, ICD9 (1979-94) and ICD10 (1995-2011).
  
  
  
  We found 16 571 encephalitis hospital admissions in the period 1979-2011, with a mean hospital admission rate of 5·97 per 100 000 per year (95% CI 5·52-6·41). Hospital admission rates declined from 1979 to 1994 (ICD9; annual percentage change [APC] -3·30%; 95% CI -2·88 to -3·66; p<0·0001) and increased between 1995 and 2011 (ICD10; APC 3·30%; 2·75-3·85; p<0·0001). Admissions for measles decreased by 97% (from 0·32 to 0·009) and admissions for mumps encephalitis decreased by 98% (from 0·60 to 0·01) after the introduction of the two-dose MMR vaccine. Hospital admission rates for encephalitis of unknown aetiology have increased by 37% since the introduction of PCR testing.
  
  
  
  Hospital admission rates for all-cause childhood encephalitis in England are increasing. Admissions for measles and mumps encephalitis have decreased substantially. The numbers of encephalitis admissions without a specific diagnosis are increasing despite availability of PCR testing, indicating the need for strategies to improve aetiological diagnosis in children with encephalitis.
  
  
  
  None.
authors.affiliation: Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK; NIHR Oxford Biomedical Research Centre, Oxford, UK; University of Oxford, Oxford, UK. Electronic address: mildred.iro@paediatrics.ox.ac.uk.
authors.forename: Mildred A
authors.initials: MA
authors.lastname: Iro
authors.affiliation: Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK; NIHR Oxford Biomedical Research Centre, Oxford, UK; University of Oxford, Oxford, UK; Vaccine Evaluation Center, BC Children's Hospital, University of British Columbia, Vancouver BC, Canada.
authors.forename: Manish
authors.initials: M
authors.lastname: Sadarangani
authors.affiliation: Unit of Health-Care Epidemiology, Nuffield Department of Population Health, University of Oxford, Oxford, UK.
authors.forename: Raphael
authors.initials: R
authors.lastname: Goldacre
authors.affiliation: Primary Care Clinical Trials Unit, Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK.
authors.forename: Alecia
authors.initials: A
authors.lastname: Nickless
authors.affiliation: Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK; NIHR Oxford Biomedical Research Centre, Oxford, UK; University of Oxford, Oxford, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Pollard
authors.affiliation: Unit of Health-Care Epidemiology, Nuffield Department of Population Health, University of Oxford, Oxford, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Goldacre
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004660:Encephalitis / Q000453:epidemiology*; D004739:England / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D017589:Immunization Programs; D007223:Infant; D007231:Infant, Newborn; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage; D010343:Patient Admission / Q000706:statistics & numerical data / Q000639:trends*; D011159:Population Surveillance; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D022542:Measles-Mumps-Rubella Vaccine