Anaphylactic reaction is the type of reaction that occurs to some people that are very reactive to certain allergens, for example, bee stings or peanuts.
Sometimes, the allergens injected in the vaccine, can trigger a similar type of reaction.
In this reaction, the throat can “close” or the bronchi (breathing lung tubes) can constrict leading to difficulty breathing. Other problems of this reaction include development of diffuse itching or even hives, swelling of the eye-lids, lips or even tongue (further compounding the difficulty breathing).
It often requires administration of Adrenaline (medication contained in the Epi-Pen®), and other medications.
