Suitability for COVID-19 vaccination based on prior allergy or current dietary practices

Ashley Marsden, Senior Medicines Optimisation Pharmacist, Pharmacy Practice Unit, Royal Liverpool HospitalPublished Last updated See all updates

Prior allergy and religious or other dietary requirements could occasionally affect suitability for vaccination, and patients will often have questions.

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

Advice end-points

Seek advice from Allergy Specialist

If no respiratory or cardiovascular compromise, and symptoms rapidly resolved with a maximum of ONE dose of IM adrenaline, individuals can receive a further dose of the SAME vaccine in any care setting.

Observe for at least 30 minutes and consider pre-treatment with a dose of non-sedating antihistamine at least 30 minutes before vaccination.

Note that pre-treatment with antihistamines may mask initial symptoms of a reaction.

Give further dose, using the SAME vaccine in any vaccination setting. Observe for at least 30 minutes.

Consider pre-treatment with non-sedating antihistamine, at least 30 minutes before vaccination

Give further dose of the SAME vaccine in any vaccination setting. Observe for at least 15 minutes.

Consider pre-treatment with non-sedating antihistamine at least 30 minutes before vaccination.

On advice of a specialist, consider administration of the implicated mRNA vaccine under medical supervision in hospital. Where reaction was to AstraZeneca vaccine, give alternative vaccine in any setting.

Observe for at least 30 minutes and consider pre-treatment with a dose of non-sedating antihistamine at least 30 minutes before vaccination.

Note that pre-treatment with antihistamines may mask initial symptoms of a reaction.

(Anaphylaxis, i.e. objective respiratory and/or cardiovascular compromise, usually with skin signs)

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.

Change history

  1. Flow chart from green book replaced with current edition
  2. Text updated to state that those with self-limiting reactions, reactions that responded to antihistamines and those with non-allergic reactions should be observed for at least 15 minutes post vaccination.
  1. Page, tool and flow chart updated to reflect changes to Green Book for management of prior allergy
  1. Context and background to decision tool added to page including flowchart from which generated
  1. COVID-19 Vaccine Prior Allergy Decision Tool added.
  1. Published