Subacute sclerosing panencephalitis in Wales.

Twenty cases of subacute sclerosing panencephalitis (SSPE) occurring over an 18-year period in Wales are described and used as the basis for a comparison of measles infection, vaccination rates and the incidence of SSPE in England and Wales. Rates of measles infection were higher in Wales in all age groups, and fewer Welsh children were vaccinated, which maintained a high risk of SSPE per case of measles. Following vaccination, there was a more pronounced change in the age distribution of measles infection in Wales than in England, and it is proposed that one contribution to the high frequency of SSPE in the 1980s was the reservoir of measles in unvaccinated 2-4-year-olds, acting as a source of infection for children aged < 2 years, in whom the risk of SSPE following measles is known to be higher than in other groups.