Recurrent hypotonic-hyporesponsive episodes after immunization with a diphtheria-tetanus-acellular pertussis-Hib component vaccine

Background: Hypotonic-hyporesponsive episodes are rare side effects which may occur in infants within a few hours after immunization with diphtheria-tetanus-toxoid (DT) or diphtheria-tetanus-pertussis (DTP) vaccine. The patients appear in a shock-like condition, become pale, limp and unresponsive. This condition lasts for minutes to hours before the infants appear normal again. No sequelae have been reported. The etiology of this phenomenon is unknown. Case: A healthy 5 month old boy experienced a first hypotonic-hyporesponsive episode 3 hours after having received his second DTP(acellular)-Hib combined immunization along with a second dose of hepatitis B vaccine. One month later he received a third dose of the same DTPa-Hib vaccine and oral Polio and again a hypotonic-hyporesponsive episode occurred. The boy's further development was normal, no sequelae have been observed. Discussion: The purpose of our report is to remind physicians of the rare possibility of a shock-like reaction after DT- or DTP immunization in infancy, which has also been observed in association with the use of the new acellular pertussis component vaccines - although less frequently than after conventional whole cell pertussis component vaccines. Furthermore, this is to our best knowledge the first report of a recurrent hypotonic-hyporesponsive episode and it suggests a predisposition for this reaction in our patient.