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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
(1983) examined a subset of the NCES data for the relation between the onset of infantile spasms and recent DT and DPT immunizations. Infantile spasms were positively associated with receipt of DT within the week prior to the date of onset but were negatively associated with receipt of DT between 1 and 4 weeks prior to the onset. The unmatched OR for all patients with infantile spasms who were exposed to DT within the 28 days prior to the onset of this condition was 0.83 (95 percent CI, 0.46-1.50). This provides strong evidence suggesting that DT does not cause infantile spasms.
The other studies in the literature that addressed this issue were uncontrolled observational studies. In the North West Thames study (Pollock and Morris, 1983), only two seizures (other than febrile seizures) were reported in association with DT immunization. These cases were found in the hospital activity analysis (case review) part of the study. Two patients with seizures with focal signs presented at 22 and 24 days, respectively, after DT immunization. Long-term follow-up of these patients was not described in the report; therefore, no information describing whether a residual seizure disorder developed was provided. However, the relatively long period of time between the receipt of DT and the development of seizures in both patients (22 and 24 days) makes a causal relation between vaccine and the event much less biologically plausible. In other uncontrolled observational studies by Pollock et al. (1984, 1985), no evidence of residual seizure disorder in association with DT was seen in children who were neurologically normal prior to immunization with DT. In the NCPP uncontrolled cohort study by Hirtz et al. (1983), no cases of residual seizure disorder were seen in association with immunization with tetanus toxoid. The one seizure recorded in temporal association with tetanus toxoid administration occurred in a child with a previous neurologic condition; the data do not make it clear whether he had residual seizure disorder.
The evidence favors rejection of a causal relation between DT and infantile spasms.
The evidence is inadequate to accept or reject a causal relation between DT and residual seizure disorder other than infantile spasms.
The evidence is inadequate to accept or reject a causal relation between tetanus toxoid or Td and residual seizure disorder.