PERTUSSIS IMMUNIZATION AND SERIOUS ACUTE NEUROLOGICAL ILLNESSES IN CHILDREN

Objective-To determine long term outcome in children who had a severe acute neurological illness in early childhood associated with pertussi s immunisation. Design-Follow up study of cases and matched controls. Setting-Assessment of children at home and at school throughout Britai n. Subjects-Children recruited into the national childhood encephalopa thy study in 1976-9 were followed up, with one of their two original m atched controls, in 1986-9. Main outcome measures-Performance in educa tional attainment tests; behaviour problems reported by teachers and p arents; continuing convulsions; evidence of other neurological or phys ical dysfunction. Results-Over 80% of cases and controls were traced. Case children were significantly more likely than controls to have die d or to have some form of educational, behavioural, neurological, or p hysical dysfunction a decade after their illness. The prevalence of on e or more of these adverse outcomes in case children who had been immu nised with diphtheria, tetanus, and pertussis vaccine within seven day s before onset of their original illness was similar to that in case c hildren who had not been immunised recently. The relative risk for rec ent diphtheria, tetanus, and pertussis immunisation in children who ha d died or had any dysfunction in comparison with controls was 5.5 (95% confidence interval 1.6 to 23.7). However, the number of cases associ ated with vaccine (12) was extremely small and statistically vulnerabl e, and other possible agents or predisposing factors could not be excl uded. Conclusions-Diphtheria, tetanus, and pertussis vaccine may on ra re occasions be associated with the development of severe acute neurol ogical illnesses that can have serious sequelae. Some cases may occur by chance or have other causes. The role of pertussis vaccine as a pri me or concomitant factor in the aetiology of these illnesses cannot be determined in any individual case. The balance of possible risk again st known benefits from pertussis immunisation supports continued use o f the vaccine.