expensive study would not be statistically powerful enough to detect the relatively rare neurologic events of interest. Data from the pilot study (Gale et al., 1990) were reviewed by the Committee to Study the Adverse Consequences of Pertussis and Rubella Vaccines; the same data have recently been published in final form (Gale et al., 1994).
Vaccine Safety Committee
After completion of the IOM report Adverse Effects of Pertussis and Rubella Vaccines (IOM, 1991) IOM convened the Vaccine Safety Committee under the mandate of the National Childhood Vaccine Injury Act. The Vaccine Safety Committee reviewed evidence about possible adverse events caused by vaccines against diphtheria, tetanus, measles, mumps, polio, hepatitis B, and Haemophilus influenzae type b. The committee's report was released in 1993 (IOM, 1994). With regard to diphtheria and tetanus toxoids and encephalopathy, the Vaccine Safety Committee concluded that the evidence favors rejection of a causal relation between encephalopathy (acute or chronic) and (a) diphtheria and tetanus toxoids for pediatric use (DT), (b) tetanus and diphtheria toxoids for adult use (Td), and (c) tetanus toxoid. The committee was not charged with reexamining the adverse effects of DPT.
THE CHARGE TO THE 1993 COMMITTEE TO STUDY NEW RESEARCH ON VACCINES
The U.S. Public Health Service, recognizing the possible significance of the newly published data from the NCES, enlisted IOM in a new assessment of the relation between DPT and permanent neurologic damage. The IOM convened the Committee to Study New Research on Vaccines in December 1993. The charge to the committee was to evaluate the contribution of the new data from the NCES to answering the question of whether DPT is causally related to permanent neurologic damage. The committee's conclusion could be phrased in terms of the impact that it might have on the conclusion of the 1991 IOM report Adverse Effects of Pertussis and Rubella Vaccines regarding the causal relation between DPT and permanent neurologic damage.
The six members of the Committee to Study New Research on Vaccines had expertise in pediatrics, neurology, and epidemiology. Each committee