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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
isolated from a few available implicated vials. That report is discussed later in this chapter.
Deaths Temporally Associated with Vaccine Administration but Clearly Caused by Something Other Than the Vaccine
Passive surveillance systems contain many reports that fall into this category. Reports to the manufacturer or to the government regarding the death of a vaccine recipient in temporal relation to vaccination can be made before a cause of death is established. Once an autopsy is performed, it is sometimes clear that the death was temporally but not causally related to vaccination. An example of such a death is one that was reported to VAERS. This report describes the death of a 5-year-old 10 days after receipt of diphtheria and tetanus toxoids and pertussis vaccine (DPT), OPV, and measles-mumps-rubella vaccine (MMR). The cause of death was Haemophilus influenzae type b meningitis, which did not appear to be vaccine related.
Deaths Classified as SIDS
For many years, the standard immunization schedule in the first year of life (the period in which most cases of SIDS occur) included only DPT and polio vaccine. Use of hepatitis B and H. influenzae type b vaccines during the first year of life is increasing rapidly. Although the scientific question of interest is, "Does vaccination increase an infant's probability of dying of SIDS," the research has focused on the role of DPT, even though polio vaccine is often given with DPT. The previous Institute of Medicine report on rubella and pertussis vaccines (Institute of Medicine, 1991) concluded that the evidence favors rejection of a causal relation between DPT and SIDS. "Studies showing a temporal relation between these events are consistent with the expected occurrence of SIDS over the age range in which DPT immunization typically occurs" (Institute of Medicine, 1991, p. 141). A few studies that primarily investigated the role of DPT in SIDS also examined the role of polio vaccine (Bouvier-Colle et al., 1989; Hoffman et al., 1987; Taylor and Emery, 1982; Walker et al., 1987). Only Hoffman and colleagues (1987) report odds ratio estimates of the relative risk of a SIDS case infant being immunized with OPV (0.57 for age-matched controls and 0.61 for age-, race-, and low-birth-weight-matched controls). These odds ratios were very similar to those obtained for the relative risk from DPT immunization. The committee's evaluation of the causal relation between diphtheria and tetanus toxoids for pediatric use (DT) and SIDS is discussed later in this chapter.
Passive surveillance systems such as the Monitoring System for Adverse Events Following Immunization (MSAEFI) and VAERS contain many