Key points

Allergic reactions to vaccines are possible based on previous allergy.

In addition, patients may ask about their suitability for vaccination based on religious or other dietary requirements or beliefs.

We’ve created a series of articles to help you advise patients when they need advice on individual vaccine suitability.

Prior allergy to COVID-19 Vaccine

Where patients have had an allergic reaction to the first dose of any COVID-19 vaccine, options for further doses will vary dependent on the nature of the initial reaction.

Our decision tool below guides you through these options.

COVID-19 Vaccine Prior Allergy Decision Tool

Background to decision tool

Advice from BSACI

The decision tool is derived from British Society for Allergy and Clinical Immunology (BSACI) advice represented in UK Health Security Agency (UKHSA – formerly known as PHE) Immunisation Against Infectious Disease (the Green Book): Flowchart for managing patients who have allergic reactions to the first dose of COVID-19 vaccine.

The flowchart and tool suggest that individuals who have had a possible reaction to the first dose of a COVID-19 vaccine may be able to receive further doses as per the management advice below:

Where symptoms began within 2 hours of the first vaccination, this could indicate an immediate-type allergic reaction:

• If the patient had anaphylaxis (i.e. objective respiratory and/or cardiovascular compromise, usually with skin signs) then seek advice from an allergy specialist. Many individuals do not react when given a dose of the same vaccine. If the reaction was to AstraZeneca the specialist may recommend complete or boost with Pfizer-BioNTech or Moderna vaccine (given in any setting, with observation for 30 minutes). If the reaction was to a mRNA vaccine, the specialist may recommend a further dose with same or alternate mRNA vaccine in a hospital setting; with observations for at least 30 minutes. Consider pre-treating with a non-sedating antihistamine, at least 30 minutes prior to vaccination. But, be aware this may mask initial symptoms of a reaction.
• If the patient had systemic symptoms but no objective symptoms of anaphylaxis e.g. no respiratory or cardiovascular compromise and symptoms rapidly resolved with a maximum of ONE dose of IM adrenaline; the patient can have a further dose using the same vaccine in any vaccination setting (observe for at least 30 minutes). Consider pre-treating with a non-sedating antihistamine, at least 30 minutes prior to vaccination. But, be aware this may mask initial symptoms of a reaction.
• If the reaction involved swelling or rash local to injection site only, the individual can have a further dose using the same vaccine in any vaccination setting; consider pre-treatment with a non-sedating antihistamine 30 minutes prior to further vaccination (but, be aware this may mask initial symptoms of a reaction) and observe for 30 minutes post vaccination.

Where symptoms began 2 or more hours after vaccination, this could indicate delayed urticaria/angioedema:

• If the reaction involved swelling or rash local to injection site only, the individual can have a further dose using the same vaccine in any vaccination setting; observe for 30 minutes; consider pre-treatment with a non-sedating antihistamine 30 minutes prior to vaccination (but, be aware this may mask initial symptoms of a reaction).
• If the reaction was self-limiting or resolved with oral antihistamine, the individual can have a further dose using the same vaccine in any vaccination setting; observe for at least 15 minutes; consider pre-treatment with a non-sedating antihistamine, 30 minutes prior to second vaccination (but, be aware this may mask initial symptoms of a reaction).
• If the reaction required medical attention, advice from an allergy specialist should be sought prior to further vaccination.

Individuals with non-allergic reactions (vasovagal episodes, non-urticarial skin reaction or non-specific symptoms) to the first dose of a COVID-19 vaccine can receive further doses of vaccine in any vaccination setting. Observation for 15 minutes is recommended.

Flowchart in Green Book

The flowchart from which the decision tool and advice above has been generated is also reproduced below with kind permission from the authors of the Green Book.

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