What We Know About Allergic Reactions to Vaccines

What We Know About Allergic Reactions to Vaccines

Food allergies play a strong role, but most people with them likely have little to worry about.

When it comes to vaccines, experiencing an allergic reaction isn’t unheard of. In fact, having trouble receiving a vaccine is common enough the Centers for Disease Control and Prevention (CDC) has a full list on its website of reasons why some people should NOT be inoculated. The list includes everything from having a previous allergic reaction to a given vaccine to being pregnant, having a weakened immune system, having a brother or sister with a problematic immune system, suffering from tuberculosis, and more. (The list is really quite lengthy).

Generally speaking, there are two main things to look out for. Basically, if your immune system is somehow compromised you should be cautious. If you are allergic to some of the ingredients used to make a specific vaccine, you should probably double check with a professional before being inoculated, as well.

What ingredients make up the offenders? Here is a general overview, plus a look at coronavirus vaccines and reactions people are having to them. Of course, always talk to your doctor about getting a vaccine if you are unsure about doing so.

Food Allergies and Vaccines

According to an article published in the Journal of the American Osteopathic Association adverse reactions to vaccines are actually common.  Allergic reactions are really quite rare, however. Real anaphylactic reactions to vaccines only happen once in every 1 million doses, experts say.

Severe allergic reactions to vaccines are usually caused by a person having a strong food allergy to a vaccine’s ingredients. Possible allergens come in a variety of forms. In vaccines they can include eggs, yeast, gelatin, casein (dairy protein), chicken protein, and milk. So, if you have a severe allergic reaction to any of these things, you could react to a vaccine containing them as well.

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What food allergens are found where? Flu, rabies, and yellow fever vaccines are grown in chick embryo fibroblast cultures. Consequently, people with egg allergies could potentially react to them, although the risk of this happening is really very low.

Furthermore, pork and beef gelatin can be found in some vaccines as a stabilizer. This can also cause a reaction. Yeast is used in hepatitis B and quadrivalent HPV vaccines, as well as the meningococcal conjugate vaccine Menveo Novartis.  So, if you and yeast do not mix well, this could be an issue.

Last but not least, milk can present a problem. If you are severely allergic to dairy, you could be cautious about taking tetanus vaccines, as well as those for diphtheria, and acellular pertussis (Tdap and DTaP). These are produced in casein, which is a dairy protein.

Is It Really a Problem?

Should you be very worried about being allergic to a vaccine? For most people, the answer to this is a firm, ‘no’. Even if you have a food allergy, it is only very minute traces of potential allergens that end up present in vaccines. While large numbers of people may experience food allergies at some point in their lifetime, very few have such severe reactions that getting vaccines presents a life-threatening situation.

Experts back this up. Larisa V. Buyantseva, MD and Alexandra Horwitz, MD from the Division of Pulmonary, Allergy and Critical Care, and the Division of Pediatric Allergy and Immunology at the Penn State Milton S. Hershey Medical Center, respectively, argue that many more people can safely receive vaccines than do, if the proper safety precautions are taken.

Reactions to the COVID-19 Vaccine

Unfortunately, some people are having a hard time, however. Some individuals are already reacting to the new COVID-19 vaccines. One of the first documented cases occurred in Dr. Hossein Sadrzadeh. This man is a physician in Boston and he had a severe allergic reaction to Moderna’s COVID-19 vaccine in late December. Sadrzadeh said he has a known severe shellfish allergy, and carries an EpiPen. He experienced dizziness and a racing heartbeat soon after getting the vaccine. He is now fine, and enjoying his immunity but not after a serious scare.

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A personal support worker in Canada has also suffered a severe allergic reaction but is now OK. Deborah Tilli passed out after receiving the vaccine and suffered from seizures. She was taken to hospital and is known to have a severe allergy to bees. Tilli is recovering but needed considerable professional attention.

In light of cases such as these, some health authorities are cautioning people with severe allergies to food or medicine-and perhaps bees- against taking a COVID-19 vaccine.


Some scientists say they feel the polyethylene glycol (PEG) present in both the Pfizer-BioNTech and Moderna vaccines could be triggering problems. This compound has never been in a vaccine before. It has, however, been used in other drugs that have been known to trigger anaphylaxis, or a life-threatening allergic reaction. We will no doubt hear more about this in the coming weeks and months as further research is done into the possible problematic ingredients in the coronavirus vaccines.

The good news is that, thankfully, most of us do not have to worry. The vast majority of people can most likely take the COVID-19 vaccines so far approved for use without reason to fear having any adverse reaction.

As mentioned above, talk to your doctor if you have worries regarding the vaccine.

For a full list of ingredients found in the Pfizer-BioNTech vaccine, check out this information from Canada.

photo credits: BlurryMe/Shutterstock.com

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