Vaccination for people who have had an adverse event following immunisation

Adverse events after vaccination sometimes occur. The term ‘adverse event following immunisation’ (AEFI) refers to any untoward medical occurrence that follows vaccination. It does not necessarily have a causal relationship with the vaccine.¹

For more details on AEFIs, including uncommon or rare AEFIs, see Adverse events following immunisation.

It is usually not possible to predict whether an individual will react to a vaccine, or whether a reaction will be mild or serious.

To minimise the risk of an adverse event following immunisation (AEFI), follow any relevant guidelines about when to use or not use certain vaccines. Pre-vaccination screening should identify people:

• who have had an AEFI 
• with conditions that are precautions or contraindications to vaccines (see Table. Pre-vaccination screening checklist) 

Consult the disease-specific chapters in this Handbook to check the relevant contraindications and precautions for each vaccine.

In general, most people who have previously had an AEFI can safely receive future vaccines from their usual immunisation provider.

Serious adverse events following immunisation (AEFIs) are extremely rare.

The definition of a serious adverse event is any untoward medical occurrence that:

• results in death
• is life-threatening
• requires inpatient hospitalisation or prolongs existing hospitalisation
• results in persistent or significant disability or incapacity,² or is a congenital anomaly/birth defect 

For people who have had a serious AEFI, it can be challenging to determine whether to revaccinate them.

Assessing the cause of an AEFI

All possible causes for an AEFI should be systematically considered, in order to conclude that the vaccine is the likely cause.³ A thorough medical assessment and relevant testing may help to identify other causes such as a pre-existing or new illness, exposure to a drug or toxin, or coincidental infection at the time of immunisation. The biological plausibility of the AEFI should be considered, as well as the timing relative to the vaccination. 

When considering future vaccination, a detailed assessment and individual discussion is required. This should take into consideration the risk of vaccination compared to risk of the disease, treatment options for the disease and likely protection from doses already given. People who have experienced a serious AEFI can usually receive further doses under close medical supervision. The exception is where the person has a contraindication, such as anaphylaxis confirmed to have been triggered by a vaccine or one of its components, or myocarditis following a COVID-19 mRNA vaccine.

Seek further advice, where appropriate, and refer the person to a specialist clinic that manages people with special vaccination requirements. Most large children’s hospitals and some large adult hospitals have specific services for this purpose.

State and territory public health authorities can provide information about specialist immunisation clinics, or the contact details for paediatricians or medical specialists with experience in managing people who have had an AEFI.

Vaccines rarely produce allergy or anaphylaxis. Overall, the risk of anaphylaxis after a single vaccine dose is about 1 case per 1 million. However, this risk varies depending on the vaccine type.^4,5

Components that may be implicated in allergic reactions

Vaccine components that are most often considered to be implicated in allergic reactions are:

• certain antibiotics
• gelatin
• egg proteins 

Yeast is rarely associated with vaccine-related allergic reactions.

People allergic to latex may be at risk from some vaccines. This is usually from latex in the equipment holding the vaccine, such as vaccine vial stoppers (bungs) and syringe plungers, not from the vaccine formulation itself. However, very few vaccine bungs contain natural latex.

Before giving the vaccine, consult the product information to check whether it contains latex. If the production information does not list the components, contact the vaccine manufacturer for details.

For more details on vaccine components, see Table. Components of vaccines used in Australia.

Assessing people for a history of allergies

Immunisation providers must assess each person for a history of allergies and previous reactions to vaccines before giving any vaccine dose.

Depending on the allergy identified, there may not be a contraindication to vaccination. For example, if a history of allergy to antibiotics is linked to β-lactams or related antibiotics, this is not a contraindication to vaccines that contain other classes of antibiotics such as neomycin, polymyxin B or gentamicin.

Previous skin-related reactions to neomycin (such as rashes) are not considered a risk factor for a severe allergic reaction or anaphylaxis to vaccines made with neomycin, because there are only trace amounts of this antibiotic in the final product.⁶

Similarly, the measles and mumps components of MMR (measles-mumps-rubella) vaccine contain only a negligible quantity of egg protein (ovalbumin). MMR vaccine is not contraindicated in people with an egg allergy, including anaphylaxis. See Vaccinating people with a known egg allergy.^7-10

People who experience an allergic reaction associated with a vaccine dose should be fully investigated to determine:

• the possible causal relationship to vaccination
• if, and under what circumstances, the person can receive repeat doses of vaccine

People who have a history of an allergic reaction to a previous vaccine dose or to a component of a vaccine may need one or more of the following:

• to be vaccinated in a facility with medical staff in attendance
• to be observed for at least 30 minutes following vaccination
• referral to an allergist/immunologist or specialist immunisation clinic

Seek specialist advice from an allergist/immunologist or specialist immunisation clinic, if appropriate. In select cases, skin prick testing or intradermal testing may be required to assess for vaccine hypersensitivity, and graded dosing may be considered to facilitate vaccination.

Contact your state or territory health authority for details of specialist immunisation clinics, or paediatricians or medical specialists with experience in managing people with adverse events following immunisation.

Influenza vaccines

In the past, a history of anaphylaxis or a serious allergic reaction to eggs was an absolute contraindication to influenza vaccination.

However, several studies now suggest that most people with an egg allergy, including anaphylaxis, can safely receive influenza vaccines that contain less than 1 μg of ovalbumin per dose^11-13 (see Influenza).

Most vaccine-associated anaphylaxis cases reported as ‘likely due to egg allergy’ happened after people received an older formulation of influenza vaccine.¹² Manufacturing has changed since then, and all influenza vaccines used in Australia contain less than 1 μg of ovalbumin per dose.¹¹ 

The amount of residual ovalbumin may vary from year to year as a result of differences in: 

• manufacturing processes
• vaccine batches 
• country of origin

Check the vaccine product information for the vaccine’s ovalbumin content before giving it to people who are egg allergic.^11,12,14,15

When vaccinating someone with an egg allergy, it is not necessary to use the split dose protocol or to vaccinate in a specific hospital-based vaccination clinic (see Influenza).

It is also not recommended to use allergy testing (such as skin testing) before influenza vaccination, because the correlation between test results and vaccine tolerance is poor.^11,12 

The guidelines of the Australasian Society of Clinical Immunology and Allergy¹¹ have detailed information about giving influenza vaccine to people with an allergy to eggs.

Measles- and mumps-containing vaccines

Measles and mumps (but not rubella or varicella) vaccine viruses are grown in chick embryo tissue cultures. However, measles- and mumps-containing vaccines contain negligible amounts of ovalbumin, and people with a known egg allergy can safely receive these vaccines (see Measles and Mumps).^7-10

Yellow fever and Q fever vaccines

Yellow fever vaccine (Stamaril) and Q fever vaccine (Q-Vax) are contraindicated in people with a known severe allergy to eggs. These vaccines contain a higher amount of ovalbumin than the currently available influenza vaccines.

People with an egg allergy needing either yellow fever or Q fever vaccination should seek specialist immunisation advice from state or territory health authorities.

See Yellow fever and Q fever.

Rabies vaccine

People with an allergy to eggs who need rabies vaccine should receive the purified Vero cell rabies vaccine (Verorab inactivated rabies vaccine) for pre- and post-exposure rabies vaccination.

People with an egg allergy should not receive the purified chick embryo cell vaccine (Rabipur inactivated rabies virus vaccine).

See Rabies and other lyssaviruses, including Australian bat lyssavirus.

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2. World Health Organization (WHO). Causality assessment of an adverse event following immunization (AEFI). User manual for the revised WHO classification (WHO/HIS/EMP/SAV). 2nd ed. Geneva: WHO; 2018. 
3. World Health Organization (WHO). Causality assessment of an adverse event following immunization (‎AEFI)‎: user manual for the revised WHO classification. 2nd ed. Geneva: WHO; 2019. https://www.who.int/publications/i/item/9789241516990
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5. Dreskin SC, Halsey NA, Kelso JM, et al. International Consensus (ICON): allergic reactions to vaccines. World Allergy Organization Journal 2016;9:32.
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10. Freigang B, Jadavji TP, Freigang DW. Lack of adverse reactions to measles, mumps, and rubella vaccine in egg-allergic children. Annals of Allergy 1994;73:486-8.
11. Australasian Society of Clinical Immunology and Allergy (ASCIA). Guidelines: vaccination of the egg-allergic individual. Sydney: ASCIA; 2017. 
12. Greenhawt MJ, Li JT, Bernstein DI, et al. Administering influenza vaccine to egg allergic recipients: a focused practice parameter update. Annals of Allergy, Asthma and Immunology 2011;106:11-6.
13. Erlewyn-Lajeunesse M, Brathwaite N, Lucas JS, Warner JO. Recommendations for the administration of influenza vaccine in children allergic to egg. BMJ 2009;339:912-5.
14. Mullins RJ, Gold MS. Influenza vaccination of the egg-allergic individual [letter]. Medical Journal of Australia 2011;195:52-3.
15. Kelso JM. Administration of influenza vaccines to patients with egg allergy: update for the 2010–2011 season [letter]. Journal of Allergy and Clinical Immunology 2010;126:1302-4.