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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
second episode, and made a full functional recovery following the third episode (J. D. Pollard, University of Sydney, Sydney, Australia, personal communication, 1993). A well-studied sural nerve biopsy during the third episode showed demyelination, onion bulb formation, and incipient hypertrophic neuropathy. The patient's lymphocytes could be induced to proliferate upon exposure to tetanus toxoid and to elaborate the lymphokine macrophage inhibition factor upon exposure to peripheral nerve homogenate, although these responses can be seen in vaccinees without GBS. Other studies of hypersensitivity to peripheral nerve antigens were not done. The immunologic basis for his sensitivity to tetanus toxoid was not demonstrated. Subsequently, since 1981, this man has experienced multiple recurrences of demyelinating polyneuropathy, most following acute viral illnesses. Plasmapheresis administered at 3-week intervals was initiated in 1986 and has continued until the time of this writing. In recent years he has remained functionally normal, but has minor residual sensory findings on examination (J. D. Pollard, University of Sydney, Sydney, Australia, personal communication, 1993).
Few cases of GBS following receipt of DT have been reported. Dittmann (1981b) noted that three instances of acute polyneuritis, presumably GBS, were reported as adverse events following administration of this vaccine. These data were based on passive reporting following the distribution of approximately 5.5 million doses of vaccine between 1950 and 1976 in the former East Germany.
The Monitoring System for Adverse Events Following Immunization (MSAEFI) lists four cases of GBS between 1979 and 1990 following vaccination with DT. VAERS lists two cases of GBS in temporal association with Td submitted between November 1990 and July 1992. Both patients simultaneously received DT and MM.
Controlled Observational Studies
Controlled Clinical Trials
There is biologic plausibility for a causal relation between vaccines and demyelinating disorders. The literature describing a possible association between GBS and tetanus toxoid, DT, or Td consists of case reports. The most convincing case in the literature is that reported by Pollard and Selby