Lack of evidence of encephalopathy related to pertussis vaccine: active surveillance by IMPACT, Canada, 1993-2002.

To assess whether pertussis-containing vaccines cause encephalitis or encephalopathy, the IMPACT network of Canadian pediatric centers screened more than 12,000 admissions for neurologic disorders between 1993 and 2002. Seven cases of encephalopathy began within 7 days after pertussis vaccination, but a more likely cause was found in each instance. No attributable case followed administration of >6.5 million doses of vaccine.