Vaccine allergy is extremely rare, but it is a frequent cause of referrals to allergists. Poor understanding of common and expected adverse effects often leads to misdiagnosis.
A study published in the Annals of Allergy Asthma and Immunology, looked at referrals to an allergy center in the United Kingdom for vaccine allergy. Over a 10 year period, they evaluated 95 patients with 103 doses of vaccines suspected of allergy. Most patients (58%) experienced skin reactions, rash, hives, itching and passing out. Other reactions, including fever, respiratory symptoms (shortness of breath, chest tightness, wheezing) and gastrointestinal symptoms (vomiting and abdominal pain.)
In this large study of patients, no allergic reactions were seen, all patients were vaccinated successfully. There were 3 local reactions (pain, swelling, redness) and 4 vasovagal episodes (passing out). There were 20 patients who had suspected egg allergy, 1/3 of them were disproven by testing for egg. The other patients were still able to receive MMR or influenza vaccines. In the MMR vaccine, the amount of egg is a small quantity to trigger an allergic reaction and it is not a contraindication for vaccination. The need to refer patients for influenza vaccination for egg allergy is no longer needed in the United States, although in some other countries (United Kingdom) a referral to an allergy specialist is recommended.
Some patients are wrongly advised to avoid all immunizations after a reaction to one vaccine only. All of them can be routinely vaccinated following standard protocols, unless an allergy to a common constituent is suspected. In latex allergy, no special precautions other than using latex free gloves are required, only confirmed severe anaphylaxis might require vaccines supplied without natural rubber. Certain vaccines contain traces of neomycin, although most antimicrobials are removed during purification. Only a single case of vaccine anaphylaxis attributable to neomycin has been reported. Gelatin allergy has also been reported that are in some vaccines.
In conclusion, routine vaccination is safe with a negligible risk of allergic reactions. There can be nonallergic reactions such as Guillain-Barre syndrome or encephalopathy, but these are not IgE-mediated and not vaccine allergies. Most, if not all patients with suspected vaccine allergy can be vaccinated successfully. If there is a suspicion of vaccine allergy, have your primary care refer you to an allergy specialist who is trained on vaccine allergy and safety. Allergists can help improve awareness and education as well as facilitate vaccinations in the few patients with confirmed allergy to vaccine and vaccine components.