The incidence of seizures following the administration of DTP vaccine at the Group Health Cooperative of Puget Sound, Seattle, has been estimated by epidemiologists at the Harvard School of Public Health, Boston, and by the Boston Collaborative Drug Surveillance Program, Waltham, Mass. For a population of children born in GHC hospitals, 1972-83, records of hospitalizations for neurologic disease and prescriptions of common anticonvulsant drugs were reviewed to establish the probable nature of the illness, the date of its onset, and the temporal relation to DTP.
Children omitted from the study for various reasons were as follows: 1) those not hospitalized nor treated with drug therapy (e.g., uncomplicated first febrile seizures and children with infantile spasms who received only ACTH and steroids as outpatients); 2) those with seizures and a history of possible predisposition due to trauma, asphyxia, malformation, metabolic defect, premature birth, CNS infection and sepsis; 3) those without a clear date of onset for the seizures or neurologic illness; 4) 8 cases of seizures beginning before immunization in the first 30 days of life; 5) 8 cases with a history of first seizures recorded at a subsequent visit; and 6) 2 cases of infantile spasms and 5 acute encephalopathies with onset recorded 30 days or more after DTP immunization.
Of 231 post-immunization first seizures selected for study without other predisposing cause in children 30 days of age or older, 55 had afebrile seizures, and 176 had febrile seizures. The incidence of recorded febrile seizures in the immediate post-immunization period was 3.7 times that in the period 30 days or more after immunization. One child suffered a prolonged status epilepticus on the evening of her third DTP shot, and neurologic sequelae included focal epilepsy at 6-yr follow-up. Six cases of first seizures occurred within 30 days of immunization, and the expected incidence without immunization in this time interval was calculated at 5.07. The authors conclude that serious neurologic sequelae of DTP immunization are extremely infrequent in otherwise healthy children. 
COMMENT. The omission of several groups of children from this retrospective epidemiological study detracts from the significance of the conclusions and estimates of incidence of DTP-related febrile and non-febrile seizures. The role of DTP as a precipitating cause in children with a predisposition to seizures and as a possible cause of infantile spasms is neglected. It is unfortunate that the study did not address the known risks of DTP in children with prior neurologic disease or predisposition to seizures including positive family history (see Ped Neur Briefs Nov 1987;1:40).