(1978), who described a 42-year-old man who developed GBS on three separate occasions (over a 13-year period) following receipt of tetanus toxoid. The relation between tetanus toxoid and GBS is convincing at least for that one individual, even though this man has subsequently experienced multiple recurrences of demyelinating polyneuropathy, most following acute viral illnesses (J. D. Pollard, University of Sydney, Sydney, Australia, personal communication, 1993). Of the other cases relating receipt of tetanus toxoid to the development of GBS, two others (Hopf, 1980; Newton and Janati, 1987) are recorded in enough detail to be accepted as GBS; one of these patients (Newton and Janati, 1987) received tetanus toxoid made by a U.S.-licensed manufacturer. Both patients were adults. Aside from the data in MSAEFI and VAERS, which generally do not provide sufficient clinical descriptions to establish the diagnosis, there is little information in the literature relating DT or Td to the development of GBS. The case series by Dittmann (1981b) describes three cases of polyneuritis following administration of Td. What the case reports cannot address is whether the frequency of cases is higher than the expected background rate of GBS. This question is difficult at best for rare adverse events and can be done only if (1) good age-specific background rates for the specific disease in question are known, (2) aggressive surveillance of adverse events is done, or (3) large controlled observational studies are done. None of this specific information is available when considering the relation between tetanus toxoid, DT, or Td and the occurrence of GBS. However, because the case by Pollard and Selby (1978) demonstrates that tetanus toxoid did cause GBS, in the committee's judgment tetanus toxoid can cause GBS.

Conclusion

The evidence favors a causal relation between tetanus toxoid and GBS.

If the evidence favors a causal relation between tetanus toxoid and GBS, then in the committee's judgment the evidence favors a causal relation between vaccines containing tetanus toxoid (DT and Td) and GBS.

Because the conclusions are not based on controlled studies, no estimate of incidence or relative risk is available. It would seem to be low.

Risk-Modifying Factors

GBS, as a separate discrete attack, recurs in a small percentage of those previously afflicted, perhaps 2 to 3 percent, and some individuals have been known to have three or four separate episodes. Other than the patient described by Pollard and Selby (1978), who experienced three attacks, each within 10-21 days of receipt of tetanus toxoid, cases of recurrence after vaccination are not documented. Nevertheless, if GBS occurs within 5 days



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