February 16, 2018

Allergy to Vaccines: Why Do People with Food Allergies React to Vaccination?

Vaccination is normally a safe and effective way to protect children and adults from serious diseases. However, some people with food allergies may develop an allergy to vaccines, as a result of exposure to food proteins.


A vaccine is a biological preparation that provides immunity against one or various diseases by stimulating the production of antibodies. Vaccines contain an agent resembling a microorganism that induces the disease, which, in most cases, is prepared from a weakened or killed microbe, or its products. When the substance gets into your body, your immune system recognizes it as a threat and destroys the agent. This is needed to stimulate the immune system to identify and eliminate any microorganisms related to this agent in future.

Vaccination is the most effective method of preventing infections. Routine vaccination, also known as routine immunization is recommended for everyone in the United States, depending on the age and vaccine history. Every year, children and adults all around the world receive millions of routine vaccines.

Immunization rarely triggers allergy symptoms. However, many of vaccines contain food proteins, which can put people with certain food allergies at an increased risk of reacting to the vaccine.

Estimated 8 percent of children in the United States are allergic to certain food products. Thus, an egg allergy is one of the most commonly occurring allergic disorders in kids. Since a lot of routine childhood vaccines contain egg protein or other food proteins, children with food allergies may experience an allergic reaction after being vaccinated. In some cases, this reaction may be severe or even life-threatening (anaphylaxis).

Food products whose traces are commonly found in routine childhood and other non-routine vaccines include egg, gelatin and yeast.

Reactions to an Egg Protein


Children allergic to eggs are at the highest risk of developing severe reactions when receiving vaccines. Egg and egg-related proteins may be present in various routine childhood vaccines, including those against flu (influenza) and measles, mumps and rubella (MMR). Besides, non-routine vaccines against yellow fever and typhoid also contain egg protein.

Influenza vaccines produced in different years or coming from different batches may contain different amounts of egg protein. Usually, people with an egg allergy should not be vaccinated against influenza. However, if you react to an allergy test but don’t experience any symptoms when eating eggs, you can safely receive the influenza vaccine.

In some cases, people with egg allergies may be recommended to take the vaccine, despite the risks. For instance, if you have severe asthma and a mild egg allergy, the benefits of vaccination may appear more important. In this situation, the process of vaccination should be closely monitored by an allergy specialist. The dose of vaccine may be given in small amount over several hours.

While the components of the MMR vaccine are developed in chick fibroblast cell cultures, the vaccine normally doesn’t contain egg protein. Therefore, people with an egg allergy, even a severe one, are not likely to react to the MMR vaccine. According to experts, the vaccine can be safely given to children and adults allergic to eggs. However, specialists recommend that the vaccination process is monitored by a doctor, in case of an emergency.

A vaccine against yellow fever is a non-routine vaccine that contains egg proteins. You should receive this vaccine, if you are traveling to Central/South America and sub-Saharan Africa. Compared to other egg-based vaccines, yellow fever vaccine has the highest amount of egg protein. It shouldn’t be given to people with egg allergy. A number of people allergic to chicken meat have also reported developing an allergic reaction after getting this vaccine. However, when the vaccination is required, egg-allergic people may be given the vaccine in small amounts over several hours, and a physician should be closely monitoring the process.

Reactions to Gelatin


Many routine childhood vaccines, including influenza, MMR, varicella (chicken-pox), and DTaP (diphtheria, tetanus and acellular pertussis), contain gelatin, which acts as a heat stabilizer. Gelatin is also found in non-routine vaccines for yellow fever, Japanese encephalitis, rabies, and other infections. Compared to egg protein traces also contained in some of the mentioned vaccines, gelatin is more likely to trigger an allergic reaction.

Therefore, if you have a history of allergic reactions to gelatin products (such as Jell-O), you shouldn’t receive any gelatin-containing vaccines. However, when the benefits of immunization outweigh the risks, these vaccines can be given to allergic people in small doses, strictly under the monitoring of a specialist.

Reactions to Yeast


Some types of vaccines are produced using yeast (Saccharomyces cerevisiae), commonly used by bakers for making bread. An example of yeast-containing vaccines is one against hepatitis B, which is a part of routine childhood immunization.

Normally, hepatitis B vaccine is not recommended for people with yeast allergy, but in some cases, vaccination is necessary. As in the case with other allergenic vaccines, those that contain yeast can be given to allergic people in small amounts over several hours, and a doctor should closely supervise the process.

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