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.