NCIt definition : Acute onset of unresponsiveness or diminished level of consciousness, associated with
loss of muscle tone and pallor or cyanosis, that occurs within 48 hours after childhood
immunizations. It is primarily associated with pertussis-containing vaccines administered
to children under two years of age.;
Alternative definition : NICHD: Acute onset of unresponsiveness or diminished level of consciousness, associated
with loss of muscle tone and pallor or cyanosis that occurs within 48 hours after
childhood immunizations. It is primarily associated with pertussis-containing vaccines
administered to children under two years of age.;