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Vaccine Allergy

Vaccination is an important tool in the prevention of disease.

Unfortunately, adverse reactions to vaccination occur and can include:

Local Site Reaction

The most common adverse reaction to vaccination is a local site reaction consisting of redness, soreness, and swelling. Such reactions can be secondary to adjuvants (e.g. aluminum) contained in vaccines which are used to increase vaccine immunogenicity. These reactions generally represent a normal inflammatory response to foreign substances.

Allergic Reaction

Infrequently, vaccination may also cause allergic reactions. The mechanisms of these reactions may involve allergy antibodyimmune complexes, as well as cell mediated immunity.

Vaccine components frequently associated with adverse reactions to vaccination include:

  • Chicken
  • Egg
  • Gelatin
  • Latex
  • Yeast
  • Thimerosal
  • Neomycin
  • Aluminum

For an up-to-date list of vaccine components, please visit the CDC’s Vaccine Excipient & Media Summary.

Allergy Antibody

Immediate type hypersensitivity reactions (type I) are characterized by the presence of allergy antibody (IgE). In genetically predisposed individuals, IgE antibody develops to certain vaccine components including chicken, egg, gelatin, latex, or yeast. When specific IgE antibodies bind one of these vaccine components, an allergic reaction develops within minutes to a few hours. This manifests as local site urticaria or a systemic reaction such as anaphylaxis. The rate of experiencing an anaphylactic reaction to vaccination is approximately one per million doses. 

Allergy to vaccine is commonly diagnosed by allergy skin testing.

Immune Complex

Immune complex mediated hypersensitivity reactions (type III) can also occur after vaccination. In this immunologic process, pre-formed antibodies bind antigen in vaccine creating immune complexes. These complexes are deposited into blood vessels, joints and other body tissue resulting in inflammation and body injury.

Arthus reaction is a type of immune complex hypersensitivity reaction that can occur after vaccination. It is characterized by local site redness, warmness, swelling, or ulceration that usually occurs hours after vaccination. Arthus reaction is considered a type of cutaneous vasculitis. Vaccines associated with arthus reactions include tetanus and diphtheria. 

Serum sickness is also a type of immune complex hypersensitivity reaction that can occur after vaccination. This reaction is characterized by rash, swelling, swollen lymph nodes, joint pain, and fever that typically occur 7-21 days after vaccination.

Immune complex hypersensitivity reactions to vaccine are diagnosed by history, exam and tests.

Cell Mediated

Delayed type hypersensitivity reactions (type IV) to vaccine can also occur. In this reaction, lymphocytes (a type of white blood cell) recognize antigen in vaccine and release factors that attract macrophages (another type of white blood cell). These different types of white blood cells cause an inflammatory reaction resulting in body injury. Manifestations of delayed type hypersensitivity reactions to vaccine most commonly include localized injection site nodules and rash. Components of vaccines associated with delayed type hypersensitivity include thimerosal, a vaccine preservative, and neomycin, a vaccine antibiotic. Aluminum contained in vaccines can also cause injection site nodules which may reflect a delayed type hypersensitivity reaction. 

Delayed type hypersensitivity reactions to vaccine are diagnosed by history, exam and tests. 


Vaccines are also associated with non-allergic adverse reactions. Such reactions include seizure, encephalopathy, encephalitis, and hypotonic-hypo responsive syndrome among others. 

Allergists are the experts in vaccine allergy and diagnose this condition by history, exam, and tests.

The goals of treatment are to identify the cause of vaccine allergy and prevent the development of allergic reaction on future vaccination. 

Treatment varies depending on the vaccine and suspected cause.

By visiting an Allergist, you too can take control of your vaccine allergy.

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