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Allergy to Vaccines

Covid Vaccine Allergy Reaction- Allergy Testing - Connecticut

Allergy to Vaccines

Covid Vaccine Allergy Reaction- Allergy Testing - ConnecticutVaccines are among the greatest achievements of modern medicine. Diseases (including Polio, Measles, Mumps, and Pertussis) that once caused significant illness and disability, have been controlled due to vaccination. On a yearly basis, more than 220 million doses of vaccines are administered in the United States on a regular basis. Though vaccines have been successfully used for many years, with the release of the new COVID vaccine, we’ve recently received a lot of questions about vaccines and vaccine reactions, in particular, to the COVID vaccine.

Vaccine Allergies

While it is common to have minor local reactions and mild symptoms such as fever following vaccination, the risk of having an anaphylactic reaction following vaccine administration is very low-approximately one in a million. Ideally, patients with suspected anaphylactic reactions following vaccination should be evaluated to investigate whether there is a specific component which caused the reaction. Reactions of the immediate type generally of consist of hives, swelling or difficulty breathing. These reactions are most often caused by an additive or other vaccine component. Generally, the reaction is not due to the microbial immunizing agent itself.

Allergic reactions to vaccines may be caused by components of the vaccine such as:

  • Latex: Latex may be found in certain packaging for vaccines.
  • Gelatin: Patients with a history of allergy to pork or beef may be more prone to reactions to gelatin. Gelatin is a component of some vaccines including that for Rabies, Varicella, MMR (Measles, Mumps and Rubella), Influenza, Yellow Fever, and Zoster.
  • Egg
  • Antibiotics (particularly neomycin)
  • Yeast

Skin testing for certain vaccine components (and with the actual vaccine that seemed to elicit the reaction) can be done to help identify the component causing a reaction. Speak with your allergist if vaccine reactions are a concern.

COVID Vaccine Reactions and Allergies

Pfizer and Modern mRNA COVID Vaccine

With the mRNA COVID vaccine (Pfizer and Moderna), it is currently thought that polyethylene glycol (PEG) may be the component in the vaccine which causes anaphylaxis. Polyethylene glycol is found in medications such as Miralax and Go-lytely, however it is not present in other available vaccines.

AstraZeneca and Johnson & Johnson COVID Vaccine

Polysorbate is the component in the AstraZeneca and Johnson & Johnson COVID vaccines thought to cause reactions. Polysorbate is a component of various medications, as well as some vaccines including those for flu, Tetanus, HPV, Hepatitis A and B, Meningococcus and Zoster.

Both polyethylene glycol and polysorbate are similar in structure, and therefore they are thought to cross-react with one another. If you have a history of an allergic reaction to a vaccine (or to the first COVID vaccine) or to a medication containing one of these components, you should consider speaking with an allergist prior to receiving the vaccine. Skin testing can be done to help determine if there is an immediate-type allergy to polyethylene glycol or polysorbate. Skin testing with the actual COVID vaccine is not being done (and is not recommended) at this time due to limited vaccine availability. For those patients who have a history of allergic reactions or anaphylaxis, they should be monitored for 30 minutes after receiving the COVID vaccine. Following COVID vaccine administration, all patients should be monitored for 15 minutes.

If you have any vaccine related concerns or a history of an allergic reaction to any of the vaccine ingredients listed above, please feel free to contact our office and we’d be happy to assist you.

Dr. Neetu Godhwani
Allergist & Immunologist
Advanced Specialty Care

(203) 830-4700 |

Advanced Specialty Care offers Allergy & Immunology appointments in Danbury, New Milford, Norwalk and Ridgefield, CT. Our Allergists provide comprehensive allergy evaluations, allergy testing, allergy treatment and more to new and existing patients of all ages, from pediatric to adult allergy patients. If you’d like to schedule an appointment or learn more about our practice, please call (203) 830-4700 or visit

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Multi-Specialty Private Practice with six locations in Fairfield County, CT