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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
oped clonic seizures and CSF pleocytosis within 12 days of receiving the Leningrad-16 SSW measles vaccine strain and died soon thereafter. (This case is discussed again in Chapter 10.)
Griffin and colleagues (1991) examined the records of a cohort of children in Tennessee enrolled in the Medicaid program who had received MMR or measles-rubella vaccine (MR) in their first 3 years of life to estimate the incidence of neuralgic outcomes. As determined from computerized records, children who were enrolled in the Medicaid program within 90 days of birth in one of four counties, who had a Tennessee birth certificate indicating a birth date within the study period (approximately 1974 to 1984), and who received during those years at least one diphtheria and tetanus toxoid and pertussis vaccine (DPT) immunization at ages 29-365 days and at least one MMR or MR immunization between 12 and 36 months of age were included in the study. Follow-up began at the time of the first MMR or MR immunization and was restricted to the first 36 months of life. Of the population of 18,364 children enrolled in the Medicaid program who received immunizations, 100 were confirmed to have had a seizure. Of these, 77 had febrile seizures (4 children had seizures between days 7 and 14 postimmunization and none were recurrent), 15 had febrile seizures (1 child had two seizures at 1 and 3 days postimmunization, and another child had a seizure at 29 days postimmunization), and 8 had seizures associated with other acute neuralgic illnesses. Most seizures occurred more than 30 days following the immunization. It is possible that there was underascertainment of seizure cases in this cohort, because only those patients for whom a medical claim was filed were counted. Thus, children who moved, went off the Medicaid program, or whose parents did not file a claim were not counted as seizure cases. The authors made no attempts to follow seizure cases for long-term problems.
Fescharek et al. (1990) described convulsions that occurred in 41 patients following administration of vaccine containing measles antigen, mumps antigen, or both. Seven of the 41 patients had convulsions that were not accompanied by fever. More detailed information was not supplied. It is not clear whether any of the convulsions represented the early signs of an RSD.
A report from the passive surveillance system used to detect adverse events following immunization in Canada provided the rates of occurrence of adverse events but not long-term outcomes (Koch et al., 1989). Included in that report were all adverse events reported prior to the end of 1988 for individuals who had received immunizations at any time in 1987. For the purposes of classification, convulsions/seizures were defined as those involving muscle contractions and a decreased level of consciousness, with or without a fever, and had to have been diagnosed by a physician. Forty-four cases were classified as convulsions/seizures following the administration of MMR; the associated rate was 9.3 cases per 100,000 doses. Although