Epidemiologic studies of measles, measles vaccine, and subacute sclerosing panencephalitis

Histories obtained in 350 of 375 clinically confirmed cases of subacute sclerosing panencephalitis (SSPE) reported to a national registry showed that 292 patients had measles and 58 had no history of measles. Forty of the latter patients received live, attenuated measles virus vaccine. In patients with a history of measles, measles illness occurred before age 2 years in 46%, and a mean of 7.0 years before onset of SSPE. In contrast, there was no relationship of SSPE with age at vaccination on 35 of the 40 patients historically associated with measles vaccine, and SSPE occurred a mean of 3.3 years after vaccination. Based on estimated national measles morbidity data and national measles vaccine distribution data, the risk of SSPE following measles vaccination (0.5 to 1.1 cases/10⁶) appears to be less than the risk following measles (5.2 to 9.7 cases/10⁶). Because live measles vaccine is highly effective in preventing measles illness and a high proportion of children in the United States have received measles vaccine, these data are consistent with the observed downward trend in SSPE incidence since 1969.