AnaphylaxisAnaphylaxisAn acute, multi-system, allergic reaction (IgE mediated) to a substance, such as vaccination, drugs, and food. Symptoms of anaphylaxis may include breathing difficulties, loss of consciousness, and a drop in blood pressure. This condition can be fatal and requires immediate medical attention. is a very rare allergic reaction (one in a million vaccinees), unexpected, and can be fatal if not dealt with adequately. Vaccine antigens and com­po­nents can cause this allergic reaction. These reactions can be localLocal (or localized)Restricted or limited to a specific body part or region. or systemicSystemicRelating to a system, or affecting the entire body or an entire organism (e.g., fever). and can include mild-to-severe anaphylaxis or anaphylactic-like responses (e.g. ge­ne­ra­li­zed urticariaUrticaria (also known as hives)The eruption of red marks on the skin that are usually accompanied by itching. This condition can be caused by an allergy (e.g., food, vaccine, drugs), stress, infection, or physical agents (e.g., heat, cold). or hives, wheezing, swelling of the mouth and throat, breathing difficulties, hypotensionHypotensionLow blood pressure. and shock). Reports of anaphylaxis are less common in low- and middle-income countries compared to high-income countries, probably because of reduced surveillance sensitivity and as the event may not be recognized (i.e. death attributed to another factor).

WHO's guidelines on recognition and treatment of anaphylaxis is included in Annex C of Mass Measles Immunization Campaigns: Reporting and investigating adverse events following immunization.71

Mass Measles Immunization Campaigns

Anaphylaxis of unknown cause and unrelated to vaccines increases during adolescence, being more common among girls. Vaccinators should be able to distinguish anaphylaxis from fainting and vasovagal syncopeVasovagal syncopeA neurovascular reaction that leads to fainting. (which is also common in adolescents), as well as anxiety and breath-holding spells, which are all common benign adverse events.


Misdiagnosis of faints and other common causes of collapse, such as anaphylaxis, can lead to inappropriate treatment (e.g. use of adrenalineAdrenalineA drug used to treat severe allergic reaction (anaphylaxis). Also a hormone produced by the adrenal gland. and failure to recognize and treat other serious medical conditions).

Distinguishing anaphylaxis from a fainting (vasovagal reaction)

  Fainting Anaphylaxis
Onset Usually at the time or soon after injection Usually some delay between 5–30 minutes after injection
Skin Pale, sweaty, cold and clammy Red, raised, and itchy rash; swollen eyes, face; generalized rash.
Respiratory Normal to deep breaths Noisy breathing from airways obstruction (wheeze or stridorStridorA whistling sound generated when breathing (usually heard on inspiration) that indicates obstruction of the trachea or larynx.)
Cardiovascular BradycardiaBradycardiaAbnormally slow heartbeat. TachycardiaTachycardiaA heart rate that exceeds the normal range for a resting heart.
Transient hypotension Hypotension
Gastrointestinal Nausea/Vomiting Abdominal cramps
Neurological Transient loss of consciousness, good response once prone Loss of consciousness, little response once prone

Using adrenaline to treat anaphylaxis

Adrenaline stimulates the heart and reverses the spasm in the blood vessels and the lung passages, reduces oedemaOedemaThe presence of an excessive amount of fluid in or around cells, tissues, or serous cavities of the body. and urticaria, thus countering the anaphylaxis. But this very potent agent can cause irregular heartbeat, heart failure, severe hypertensionHypertensionHigh blood pressure. and tissue necrosisNecrosisThe death of living cells or tissues. if used inappropriately, although not when treating true anaphylaxis.

The expiry date of adrenaline should be written on the outside of the emergency kit. Adrenaline that has a brown tinge must be discarded.

Key point

Each vaccinator who is trained in the treatment of anaphylaxis should have rapid access to an emergency kit with adrenaline, and be familiar with its dosage and administration.