Safety Experience with a Monocomponent Acellular Pertussis Vaccine:No Reported Hypotonic-Hyporesponsive Episodes in >50,000 Infants † 921

Results from several clinical trials involving acellular pertussis vaccines containing one or more pertussis antigens have demonstrated these vaccines to have fewer local and systemic reactions than whole-cell pertussis vaccines. However, true rates of less common serious adverse reactions, e.g. hypotonic-hyporesponsive episodes (HHE), known to be associated with whole-cell vaccines have yet to be determined. In a clinical trial of multicomponent acellular pertussis vaccines in Sweden with 80,000 participants the incidence of HHE requiring hospitalization was about one in 3,000 (Heijbel H et al., Dev Biol Stand 1997:89:101).