Serious
neurological disorders reported following whole-cell
pertussis in comparison to acellular
pertussis vaccines were evaluated. The
Vaccine Adverse Events Reporting System (VAERS) was analyzed for Emergency Department (ED) visits, life-threatening reactions, hospitalizations, disabilities, deaths,
seizures,
infantile spasms,
encephalitis/
encephalopathy,
autism,
Sudden Infant Death Syndrome (
SIDS) and
speech disorders reported with an initial onset of symptoms within 3 days following whole-cell
pertussis and acellular
pertussis vaccines among those residing in the US from 1997 to 1999. Controls were employed to evaluate potential biases in VAERS. Evaluations as to whether whole-cell and
acellular vaccines were administered to populations of similar age and sex were undertaken because these factors might influence the study's results. Statistical increases were observed for all events examined following whole-cell
pertussis vaccination in comparison to acellular
pertussis vaccination, excepting
cerebellar ataxia. Reporting biases were minimal in VAERS, and whole-cell and acellular
pertussis vaccines were administered to populations of similar age and sex.
Biologic mechanisms for the increased reactogenicity of whole-cell
pertussis vaccines may stem from the fact that whole-cell
pertussis vaccines contain 3,000 different
proteins, whereas DTaP contains two to five
proteins. Whole-cell
pertussis vaccine contains known
neurotoxins including:
endotoxin,
pertussis toxin and
adenylate cyclase. Our results, and conclusions by the US Institute of Medicine, suggest an association between serious
neurological disorders and whole-cell
pertussis immunization. In light of the presence of a safer and at least equally efficacious acellular
pertussis vaccine alternative, the Japanese and US switch to using acellular
pertussis vaccine seems well justified. Other countries using whole-cell
pertussis-containing
vaccines should consider following suite in the near future.