Hypotonic and hyporesponsive episodes after diptheria-tetanus-acellular pertussis vaccination.

Administration of the discontinued diphtheria-pertussis-tetanus vaccine was occasionally associated with a hypotonic-hyporesponsive episode in infants. The whole bacterial cell pertussis component was the likely culprit. For this reason, an acellular pertussis component was developed and incorporated into a new vaccine commonly called diptheria-tetanus-acellular pertussis (DTaP). Administration of DTaP vaccine has been followed by remarkably few hypotonic or hyporesponsive episodes. This report describes one of these unusual events.