Table 1.

Proposed Definition of HHE

Inclusion criteria
 Sudden onset of
  Limpness or hypotonia
  Reduced responsiveness or hyporesponsiveness
  Pallor or cyanosis (or failure to observe or to recall skin   coloration)
 Age <10 y
 Onset of event within 48 h of vaccination
 Duration of episode from 1 min to 48 h
Exclusion criteria
 Known cause of above signs (eg, postictal)
 Urticaria, wheezing or anaphylaxis during episode
 Normal skin coloration throughout episode