Measles, measles vaccination, and risk of subacute sclerosing panencephalitis (SSPE).

Between the years 1968 and 1979, 87 cases of subacute sclerosing panencephalitis (SSPE) appeared among the Israeli-born population. The incidence of SSPE dropped sharply in 1977, 10 years (the median age at onset of SSPE) after introduction of mass antimeasles vaccination, and remained low in 1978 and 1979. Most of the SSPE cases reported measles at an age significantly younger than that of the general population. This pattern did not change after introduction of antimeasles vaccination. Incidence was significantly lower (p less than 10(-9) in the vaccinated population than in the unvaccinated population. Occurrence of SSPE in some children who were vaccinated against measles could be explained by incomplete vaccine efficacy, or by older age at vaccination, which allows the possibility of prior exposure to measles. There was no indication that measles vaccine can induce SSPE.