A specific type of measles encephalopathy, immunosuppressive measles encephalopathy (IME), has been documented in two immunosuppressed children following vaccination against measles. IME is distinct from acute measles encephalitis and subacute sclerosing panencephalitis. It has an incubation period of 5 weeks to 6 months. In one case of a 7-year-old girl with acute lymphoblastic leukemia (Valmari et al., 1987), measles virus was isolated from her CSF approximately 10 weeks after she received MMR (which contains the more attenuated measles vaccine used in the United States). The authors believed the isolated virus was vaccine strain rather than the wild-type strain because the child had no contact with natural measles during the 5 weeks to 6 months prior to the onset of symptoms. A previously described case of IME in a leukemic child involved the Schwarz strain vaccine virus (Mitus et al., 1962). Measles virus was cultured from throat and conjunctiva, but not from postmortem brain tissue.

Controlled Observational Studies

The National Childhood Encephalopathy Study, a case-control study described in detail in Chapter 5, reported a significant association between measles vaccination and onset of either convulsions or encephalopathy within 7 to 14 days of receiving the vaccine (Alderslade et al., 1981). However, a separate analysis of those diagnosed with encephalitis or encephalopathy was not performed

Controlled Clinical Trials

A report from India (Kumar et al., 1982) described 206 children injected with the Schwarz strain of measles vaccine and 206 children who were not immunized. A 14-month-old girl was diagnosed with encephalitis (fever, vomiting, semi-consciousness, weakness, occasional white blood cells in the CSF) on postvaccination day 10. At the time the report was published, she was reported to be recovering "gradually." There were no cases of encephalitis in the controls, but the numbers are far too small to detect an association.

Causality Argument

There is demonstrated biologic plausibility that measles vaccine might cause encephalopathy. Although there are a number of reports of encephalitis or encephalopathy following immunization with measles vaccines of various strains, the rates quoted are impossible to distinguish from background rates. Good case-control or controlled cohort studies of these conditions in similar unvaccinated populations, which are necessary for deter-



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