[Hypotonic-hyporesponsive episode (HHE) following vaccination with a combined vaccine against diphtheria, tetanus and pertussis (whole cell vaccine -DTPv)].

The combined vaccine against diphtheria, tetanus and pertussis containing the whole cell component of pertussis (DPTw) is characterized by high effectiveness but is also one of the most reactogenic vaccines. Adverse events following this vaccine includes a hypotonic-hyporesponsive episode, however this episode is not well known to general practitioners and pediatricians, so the data about its incidence are not reliable. The aim of this study was to characterize the clinical features of HHE following DTPw vaccine, to estimate the ability to diagnose this syndrome by GPs and pediatricians and to assess the registration system of HHE in Poland. The studied group consisted of 49 children, patients of the Regional Consultation Polyclinic in Kraków in the years 1997-2002, in whom HHE was diagnosed. The following were analysed: sex and age, interval between vaccination and HHE, relationship to the number of DTPw doses, duration of HHE and, based on the referral, the diagnosis made by a GP. The average age of children at the moment of HHE was 3.4 months, but 46/49 children were under 6 months. The symptoms of HHE occurred after a few minutes to 48 hours after vaccination and in two children similar episodes were observed on the 6th day after vaccination, which is not consistent with the definition of HHE. Most often HHE was observed after the first (21/49) and the second (16/49) dose of DTPw. In two children HHE occurred twice, after two consecutive doses of DTPw. In four cases only GPs referring patients have diagnosed HHE. Thirty children from the studied group were further vaccinated against diphtheria, tetanus and pertussis. 61 doses of DTPa (a vaccine with acellular pertussis component) were used and in no case was the adverse event observed. Based on the results obtained it has been concluded that some difficulties are observed in the diagnosis of HHE made by GPs and pediatricians, therefore the number of HHE cases registered in Poland decreased. Hypotonic-hyporesponsive episode should be taken into consideration in differential diagnosis of the nervous system diseases. Therefore, it is extremely important to ask parents about the history of vaccinations in their children.