Clinical feature

Vasovagal episode



  • Immediate, usually within minutes of, or during, vaccine administration
  • Usually within 15 minutes of vaccine administration, but can occur within hours

Respiratory symptoms or signs

  • Normal breathing; may be shallow, but not laboured
  • Cough
  • Wheeze
  • Hoarseness
  • Stridor
  • Signs of respiratory distress, such as abnormally rapid breathing (tachypnoea), cyanosis or rib recession
  • Upper airway swelling (eg lip, tongue, throat, uvula, larynx)

Cardiovascular symptoms or signs

  • Bradycardia
  • Weak/absent peripheral pulse
  • Strong carotid pulse
  • Hypotension — usually transient and corrects in supine position
  • Loss of consciousness — improves once supine or in head-down position
  • Tachycardia
  • Weak/absent carotid pulse
  • Hypotension — sustained and no improvement without specific treatment (Note: In infants and young children, limpness and pallor are signs of hypotension)
  • Loss of consciousness — no improvement once supine or in head-down position

Skin symptoms or signs

  • Generalised pallor
  • Cool, clammy skin
  • Pruritus (skin itchiness)
  • Generalised skin erythema (redness)
  • Urticaria (weals)
  • Angioedema (localised or general swelling of the deeper layers of the skin or subcutaneous tissues)

Gastrointestinal symptoms or signs

  • Nausea or vomiting
  • Abdominal cramps
  • Diarrhoea
  • Nausea or vomiting

Neurologic symptoms or signs

  • Person feels faint or light-headed
  • Person has a sense of severe anxiety and distress

Note: Anaphylaxis features are modified from The Brighton Collaboration Case Definition Criteria for Anaphylaxis.5 Neurologic symptoms are not listed in this case definition.5 However, symptoms of anxiety and distress, including feelings of impending doom, are reported in people experiencing anaphylaxis.6

Last updated: 
7 June 2018
Last reviewed: 
7 June 2018