过敏和免疫

背景

An allergy is an abnormal immune response, a hypersensitivity, to a particular trigger or allergen. Examples of triggers/allergens include foods, mould, dust mites, pollen, insects and medications (including vaccines).

Hypersensitivity responses can vary in severity. Following a vaccine they can present as:

• urticarial – a red, itchy skin rash, often referred to as hives, that characteristically has a central raised white wheal surrounded by an area of redness
• non‑urticarial rash – skin changes that do not 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, respiratory and/or cardiovascular systems.

Some hypersensitivity responses that occur following vaccination are common, and may not preclude future doses. Severe allergic reactions involving anaphylaxis, sometimes referred to as true allergies, are rare.

Diagnosis and treatment

Distinguishing anaphylaxis from acute stress responses (including vasovagal, i.e. fainting) is often difficult. However, there are distinct, subtle differences.

If symptoms of anaphylaxis occur, immediate treatment should be provided, refer to 澳大利亚免疫手册：免疫接种后的不良事件.

Taking tryptase levels is 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, testing is 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.

A true vaccine allergy (anaphylaxis), which will be a contraindication for future doses, can only be diagnosed after specialist consultation with a vaccine allergy specialist. A specialist will often determine a diagnosis after testing or a vaccine challenge is carried out under supervision.

Association and incidence

Suspected hypersensitivity responses, particularly non‑urticarial skin rashes following a vaccine, are common. However, confirmed allergy, where a person is contraindicated from being immunised with the same vaccine in the future, is rare (less than 1 case per million doses).

If a person experiences a hypersensitivity response following vaccination, it may be related to a specific vaccine or a component in a vaccine.

Eggs

Certain vaccines (e.g. some 流感 vaccines, 麻疹死亡率/V vaccines, 黄热病, Q fever) are manufactured using chicken eggs/tissue cultures.

The amount of residual ovalbumin (egg protein) found in influenza and MMR/V vaccines is not significant, and does not increase the risk of allergic reactions in those with egg allergy (even known egg anaphylaxis). People with egg allergy can receive influenza and MMR/V vaccines safely in community vaccination settings without the need for additional monitoring,

Due to the higher ovalbumin content in the yellow fever (Stamaril) and Q‑fever vaccines, administration is contraindicated in egg‑allergic individuals. However, due to the serious nature of the disease and some countries requiring proof of immunisation as an entry requirement, the Australian Immunisation Handbook recommends that people requiring these vaccines seek specialist input from an immunologist or allergist. Researchers from the National Centre for Immunisation Research and Surveillance (NCIRS) and the Royal Children’s Hospital in Melbourne have published a 案例系列 proposing that skin testing may not be required for patients with mild egg allergy, and that a 2‑step graded challenge under medical supervision is a safe alternative.

Polyethylene glycol (PEG)

PEG is an ingredient commonly used in hand sanitisers, cosmetics, bathroom products and medications (including colonoscopy preparation products). It is also used in the manufacture of mRNA COVID-19 vaccines (Comirnaty (Pfizer) and Spikevax (Moderna)).

It is recommended that people with a history of confirmed or suspected allergy to PEG seek specialist advice from an immunology, allergy or vaccine specialist prior to vaccination. Administration of vaccines containing PEG to individuals with known anaphylaxis to PEG is contraindicated.

Gelatine

Gelatine is a protein product derived from collagen. It is also a stabilising agent used in the manufacture of some vaccines. The type of gelatine used in vaccines (usually porcine in origin) is different from the gelatine used in foods (usually bovine in origin) and is highly purified.

The incidence of anaphylaxis to gelatin is extremely low, and reactions may depend on whether the gelatine is ingested, injected (e.g. during vaccine administration) or used as an intraoperative hemostatic agent (e.g. surgical Gelfoam). Individuals with severe allergy to gelatine should seek expert advice before receiving any vaccine containing gelatine.

对未来剂量的影响

Confirmed anaphylaxis to a previous dose of a vaccine and/or confirmed anaphylaxis to a component of a vaccine is a contraindication for future administration.

See sections above for future dose implications relating to suspected or known egg, PEG and gelatine allergies.

Any suspected immunisation hypersensitivity or allergic responses following vaccination should be reported to the adverse event reporting service in your jurisdiction.

常见问题

资源

• Australian Immunisation Handbook: Table. Components of immunisation products used in Australia
• Australian Society of Clinical Immunology and Allergy: ASCIA Guidelines – Vaccination of the egg‑allergic individual
• Leong P, Al-Harrasi M, Carr B, Leahy E, Bardin PG, Barnes S. Vocal cord dysfunction/inducible laryngeal obstruction(s) mimicking anaphylaxis during SARS-CoV-2 (COVID-19) vaccination. J Allergy Clin Immunol Pract. 2022;10(5):1380-1381. doi:10.1016/j.jaip.2022.02.025
• Gold MS, Amarasinghe A, Greenhawt M, et al. Anaphylaxis: Revision of the Brighton collaboration case definition. 疫苗. 2023;41(15):2605-2614. doi:10.1016/j.vaccine.2022.11.027
• 澳大利亚免疫手册：免疫接种后的不良事件