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Lancet Infect Dis. 2017 Mar 1. pii: S1473-3099(17)30114-7. doi: 10.1016/S1473-3099(17)30114-7. [Epub ahead of print]
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.
Iro MA1 Sadarangani M2 Goldacre R3 Nickless A4 Pollard AJ5 Goldacre MJ3.
Abstract
BACKGROUND:
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.
METHODS:
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).
FINDINGS:
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.
INTERPRETATION:
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.