vaccine, introduced in the United States in 1963. However, a report of data from the National Registry for Subacute Sclerosing Panencephalitis showed that the proportion of newly diagnosed cases of SSPE occurring in children identified by history as vaccinated against measles increased approximately threefold from 1967 to 1974 (Modlin et al., 1977). These data are discussed in more detail below.

The first publication in 1972 of data in the newly established National Registry for Subacute Sclerosing Panencephalitis in the United States reported 14 patients (of a total of 219 records in the registry) who had received a measles vaccine prior to the onset between 1960 and 1970 of SSPE (Jabbout et al., 1972). Six of the 14 patients were reported to have had measles prior to the onset of SSPE as well. The interval between vaccination and the onset of SSPE was 1 year or more in all 14 cases. The specific type of measles vaccine administered is not known.

The committee was charged with investigating a possible causal relation between measles vaccine only and SSPE.

Evidence for Association

Biologic Plausibility

SSPE is a recognized sequela of measles infection, and it is biologically plausible that it could occur after administration of the live attenuated viral vaccine. Identification of the cause of SSPE as wild-type or vaccine-strain measles virus has not been possible. The viruses isolated from patients with SSPE differ from the known measles viruses. The viruses may have become altered by the prolonged residence in the brains of the patients, or they may have been different at the time of the original infection.

Case Reports, Case Series, and Uncontrolled Observational Studies

The first published case report of SSPE in a child with a history of vaccination with live attenuated measles vaccine appeared in 1968 and was described above (Schneck, 1968). In the following 5 years, several more reports of SSPE in individuals vaccinated against measles appeared (Cho et al., 1973; Gerson and Haslam, 1971; Jabbour et al., 1972; Klajman et al., 1973; Landrigan and Witte, 1973; Parker et al., 1970; Payne et al., 1969). These reports represented a total of 22 patients with SSPE, 7 of whom had a history of both measles and measles vaccination (Gerson and Haslam, 1971; Jabbour et al., 1972). The other 15 patients had a negative history for measles and a positive history for receipt of live attenuated measles vaccine (Cho et al., 1973; Jabbour et al., 1972; Klajman et al., 1973; Landrigan and Witte, 1973; Parker et al., 1970; Payne et al., 1969; Schneck, 1968). For



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