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DPT Vaccine and Chronic Nervous System Dysfunction: A New Analysis
immunizations. The newly published data from the NCES indicate that children who experience a serious acute neurologic illness are at increased risk for death or dysfunction 10 years later. Furthermore, although these data do not identify a unique “post-DPT” syndrome of long-term dysfunction, they do suggest that children who experience serious acute neurologic illnesses (as described in the original NCES as encephalopathies or as severe or complicated convulsions) within 7 days after DPT vaccination are at no different risk of experiencing a broad range of long-term dysfunctions (neurologic, behavioral, educational, motor, sensory, and self-care dysfunctions) than are all other children who experience similar serious acute neurologic illnesses. Because the NCES is the only systematic study of long-term dysfunctions after immunization with DPT, the committee can comment only on the causal relation between DPT and those long-term dysfunctions studied by the NCES (Madge et al., 1993; Miller et al., 1993).
Thus, the committee concludes that some children who receive DPT and who experience a serious acute neurologic illness within 7 days thereafter would be expected to go on to experience chronic nervous system dysfunction or die. (All subsequent discussions of the risk of chronic nervous system dysfunction following serious acute neurologic illness should be interpreted to include the risk of death as a sequela to the acute illness.) The committee concludes that this might be true, but within and only within the confines of the conditions (acute and chronic) studied by the NCES. There is no evidence to suggest whether children who receive DPT and do not experience a serious acute neurologic illness are at increased risk for long-term dysfunction.
The NCES did not identify clinical findings that differentiated the post-DPT group from others who had presented earlier with an acute neurologic disorder. Moreover, the fact that the acute and chronic nervous system dysfunctions identified in the NCES are so heterogeneous is compatible with the possibility that DPT vaccination may “trigger ” acute neurologic signs and symptoms in children with underlying brain or metabolic abnormalities. It is possible that the chronic nervous system dysfunction described by the NCES is the result of an underlying abnormality rather than the acute encephalopathy. It is important to note that the NCES does not provide evidence of a direct relation between DPT and chronic nervous system dysfunction, that is, in the absence of a serious acute neurologic illness that occurs within 7 days after receiving DPT. The NCES does provide data on one special or limited case of a possible relation between DPT and chronic nervous system dysfunction, situations in which a serious acute neurologic illness follows DPT vaccine within 7 days.
The committee posits three plausible scenarios whereby the acute neurologic illnesses that follow DPT might be related to chronic nervous system dysfunction. Before discussing these three scenarios and the implications for causality and risk, the committee notes that the NCES data do not permit an