Since pertussis vaccines were introduced in the 1940s, physicians have recognized their association with adverse events, and this association has continued to the present time.
Today we use whole-cell vaccines made up of killed inactivated organisms of Bordatella pertussis that contain a multitude of antigens, some of which induce protection to severe whooping cough. Several of these materials, such as endotoxin, may account for these vaccines' reactogenicity. Commonly reported minor reactions include pain and swelling at the injection site, fever, and vomiting. More worrisome to parents and physicians are episodes of somnolence, febrile seizures, unusual prolonged screaming, and hyporesponsive-hypotonic episodes; yet none of these has been demonstrated to be associated with permanent sequelae.1
Rabinovich R, Robbins A. Pertussis VaccinesA Progress Report. JAMA. 1994;271(1):68-69. doi:10.1001/jama.1994.03510250084042