Background

Hypersensitivity/allergic reactions following immunisation can be classified as:

  • Urticarial – a red, itchy skin rash often referred to as hives, which characteristically has a central raised white wheal surrounded by an area of redness
  • Non-urticarial rash – skin changes that don’t involve hives
  • Angioedema – swelling in the deeper layers of the skin
  • Generalised allergic reaction – involving symptoms like vomiting and diarrhoea
  • Anaphylaxis – a sudden onset and rapid progression of symptoms involving the skin, as well as systemic symptoms respiratory and/or cardiovascular systems

Suspected hypersensitivity reactions, particularly non-urticarial skin rashes following immunisation, are common, however true vaccine allergy, where a person is contraindicated from being immunised with the same vaccine in the future, is rare (in most studies reported as less than 1 case per million doses). For further information on diagnosing hypersensitivity reactions and anaphylaxis please refer to Guidance for differentiating anaphylaxis and acute stress response for vaccine providers.

Post-licensure surveillance of COVID-19 vaccines show anaphylaxis following administration of Vaxzevria (AstraZeneca) occurring at similar rates to routine vaccines [refer to TGA: AstraZeneca ChAdOx1-S COVID-19 vaccine].  Anaphylaxis following Comirnaty (Pfizer), whilst still extremely rare, occurs at a slightly higher rate of approximately 4.7 cases per million doses. Data from the US has shown that Spikevax (Moderna) has a rate of anaphylaxis with approximately 2.5 cases per million. Most of these cases (89%) occurred within 30 minutes of vaccination and 26% had a history of prior anaphylaxis.

A confirmed vaccine allergy usually requires a specialist consultation with a vaccine allergy specialist, often with specific testing or a vaccine challenge under supervision.

All COVID-19 immunisation hypersensitivity/allergic reactions should be reported to your state’s vaccine safety reporting service. In Victoria this is SAEFVIC. SAEFVIC staff may direct the report to an immunisation specialist or alternatively to a vaccine allergy specialist within the VicSIS network (a network of specialist immunisation clinics in Victoria), as appropriate.

Allergy to components of COVID-19 vaccines

Polyethylene Glycol (PEG)

PEG is an ingredient contained in mRNA COVID-19 vaccines (Comirnaty (Pfizer) and Spikevax (Moderna)). It is also a commonly used ingredient of other medications, hand sanitisers, cosmetics, bathroom products and colonoscopy preparation products, routinely used within Australia. Whilst it is uncertain whether PEG contained in mRNA vaccines may trigger anaphylaxis, additional precautions are required prior to administration.

It is recommended people with a history of confirmed or suspected allergy to PEG seek specialist advice from an immunology/allergy/vaccination specialist regarding the safety of vaccination.

NB: Vaccination with the Comirnaty (Pfizer) and Spikevax (Moderna) is contraindicated in people with documented anaphylaxis to PEG.

Polysorbate 80

Polysorbate 80 is chemically related to Polyethylene Glycol and is an ingredient in both Vaxzevria (AstraZeneca) and Nuvaxovid (Novavax).

If there is a history of confirmed or suspected allergy to Polysorbate 80 it is recommended that specialist advice be sought from an immunology/allergy/vaccination specialist regarding the safety of administering either vaccine.

NB: Vaccination with Vaxzevria (AstraZeneca) or Nuvaxovid (Novavax) is contraindicated in people with documented anaphylaxis to Polysorbate 80.

Latex

All of the COVID-19 vaccines available for use within Australia (Vaxzevria (AstraZeneca), Comirnaty (Pfizer), Spikevax (Moderna) and Nuvaxovid (Novavax)) can both be administered to people with latex allergies following standard precautions, with a 15-minute post-vaccination observation period.

COVID-19 vaccines and allergies

Reaction following a previous dose of a COVID-19 vaccine

The only two absolute contraindications to vaccination are anaphylaxis to a previous dose of the same vaccine or anaphylaxis to a component of the vaccine.

Additional precautions are recommended for individuals with possible allergic reactions to a previous dose of a COVID-19 vaccine. In this instance, a specialist review by an immunology/allergy/vaccination specialist to undertake a risk/benefit assessment to assess suitability for further vaccination should be undertaken.

If an individual experiences anaphylaxis after being vaccinated with one type of COVID-19 vaccine, this does not preclude them from having another type following the additional precautions above. If there is a high risk of an allergic reaction to one of the COVID-19 vaccines due to an existing allergy to PEG or Polysorbate 80 it may be possible to a have a COVID-19 vaccine that does not contain the ingredient, depending on availability and with appropriate medical advice.

COVID-19 vaccination in people with allergic conditions

For patients with a history of anaphylaxis to food, drugs, venom or latex, it is recommended a routine observation period of 15 minutes following COVID-19 vaccination is observed.

If a patient has a history of a known systemic mast cell activation disorder with raised mast cell tryptase that has required treatment, a referral to VicSIS prior to vaccination is recommended.

Please refer to COVID-19 vaccination – ATAGI clinical guidance on COVID-19 Vaccine in Australia in 2021 or the ASCIA Allergy, Immunodeficiency, Autoimmunity and COVID-19 Vaccination Position Statement for more information.

Delayed urticaria following a COVID-19 vaccine

Acute urticaria can occur 1-2 weeks following vaccination. The symptoms can last on average 3-4 weeks but may resolve more rapidly. The urticaria can be generalised and intensely itchy. Symptoms can be managed with age-appropriate doses of non-sedating over-the-counter antihistamines (tablets or liquid) up to 4 times per day (such as cetirizine, loratadine, fexofenadine or desloratadine), best given in spaced intervals. This type of urticaria with onset that is delayed after the vaccination is generally not an indication of reproducible allergy to the vaccine and therefore investigations are not indicated. Future vaccinations can be given in a routine environment, with a 15-minute post vaccination observation period. If symptoms develop within 24 hours of vaccination, persist beyond two weeks, or there are additional concerns, then review by an immunisation specialist or allergist could be considered.

Management following anaphylaxis to a COVID-19 vaccine

Should symptoms of anaphylaxis occur immediate treatment should be provided [refer to Australian Immunisation Handbook: Adverse events following immunisation]

Investigations

Tryptase levels are recommended following potential allergic reactions as they assist with allergy assessment. Normal tryptase levels are reassuring. Tryptase levels are recommended 1 hour, 4 hours and 24 hours post reaction, however, if this is not possible, it recommended once an individual presents to an emergency department and is stable and then just prior to discharge in the case of a short admission.

It is recommended that EpiPens only be prescribed by an allergy/immunology specialist following a review. This is based on the following:

  • vaccines can be easily avoided and EpiPens are on the Pharmaceutical Benefits Scheme for indications that cannot be avoided
  • a prescription of an EpiPen has been shown to increase anxiety in people once it is prescribed even if it is not clinically indicated, which is thought to be due to the perceived uncertainty of future reactions.

Resources:

Authors: Rachael McGuire (MVEC Education Nurse Coordinator), Nigel Crawford (Director, SAEFVIC, Murdoch Children’s Research Institute), Daryl Cheng (Paediatrician, The Royal Children’s Hospital), Francesca Machingaifa (MVEC Education Nurse Coordinator), Sara Barnes (Head of Allergy, Monash Health) and Adele Harris (Research Nurse, SAEFVIC, Murdoch Children’s Research Institute)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator)

Date: November 30, 2022

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly review materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.