Updated July 30, 2015.

Millions of routine childhood vaccinations are given every year in the United States; allergic reactions from these vaccines are extremely rare. However, some people with certain food allergies may be at higher risk for allergic reactions as a result of vaccines containing certain food proteins.

Up to 8% of children suffer from food allergies, with egg being one of the most common foods to which children are allergic.

Many routine childhood immunizations contain traces of egg protein or other food ingredients. As a result, there is the possibility that a child with food allergies will experience anaphylaxis (a severe allergic reaction) as a result of receiving a vaccination.

The following foods are present in small amounts in routine childhood vaccines; other non-routine vaccines containing food proteins are also listed.

Egg

Children with egg allergy present the biggest concern when receiving childhood vaccines. The following routine childhood immunizations may contain egg or egg-related proteins: influenza (flu) and measles-mumps-rubella (MMR) vaccines. In addition, the following non-routine vaccines contain egg protein: yellow fever and typhoid vaccines.

Influenza vaccine contains limited amounts of egg protein, and this amount may vary from year to year and batch to batch. In general, the influenza vaccine should not be given to people with a true egg allergy (people who have a positive allergy test to egg but can eat eggs without experiencing any symptoms are not egg allergic).

However, in certain situations, the benefit of receiving this vaccine may outweigh the risks; this may be the case in people with severe asthma and mild egg allergy. In these cases, an allergist may be able to give the vaccine in small amounts over many hours, while closely monitoring the person for an allergic reaction.

The MMR vaccine is produced in chick fibroblast cell cultures; the vaccine likely does not contain egg proteins to which a person with egg allergy would react. Most people, even those with a severe egg allergy, do not have an allergic reaction to the MMR vaccine. Therefore, the American Academy of Pediatrics recommends that children with egg allergy can be given the MMR vaccine without any special measures being taken. It would be reasonable, however, to monitor an egg-allergic child in the physician’s office for a period of time after giving the MMR vaccine.

Yellow fever vaccine, a non-routine vaccine given to people traveling to Central/South America and sub-Saharan Africa, does contain significant amounts of egg proteins and should not be given to people with egg allergy. Yellow fever vaccine, which contains the highest amount of egg protein of all the egg-based vaccines, has also been reported to cause allergic reactions in people with an allergy to chicken meat. Similar to influenza vaccine, the yellow fever vaccine may be able to be given to egg-allergic people in small amounts over many hours, under close monitoring by a physician.

Gelatin

Gelatin, like that found in Jell-O, is added to many vaccines as a heat stabilizer. Routine childhood vaccines containing gelatin include MMR, varicella (chicken-pox), influenza and DTaP (diphtheria, tetanus and acellular pertussis). Non-routine vaccines containing gelatin include yellow fever, rabies, and Japanese encephalitis. Allergic reactions to the MMR vaccine are far more likely due to the gelatin in the vaccine rather than to residual egg proteins in the vaccine.

Essentially, any person who has experienced an allergic reaction after eating gelatin food products (Jell-O) should not be given any of the above vaccines. However, as is the case with egg-containing vaccines in egg-allergic people, gelatin-containing vaccines may be able to be given to gelatin-allergic people under the direct supervision of a physician.

Baker’s Yeast

Certain vaccines are synthesized by Saccharomyces cerevisiae, which is the common bakers' yeast used for making bread. Routine childhood vaccines containing baker’s yeast include hepatitis B, and any combination vaccine that contains hepatitis B.

Any person who has experienced an allergic reaction after eating food products containing baker’s yeast should not be given hepatitis B vaccine. However, as is the case with egg-containing vaccines in egg-allergic people, yeast-containing vaccines may be able to be given to yeast-allergic people under the direct supervision of a physician.

Learn more about the basics of food allergies, and the most common food allergies in children.

_Sources:

Moylett EH, Hanson IC. Mechanistic Actions of the Risks and Adverse Events Associated with Vaccine Administration. J Allergy Clin Immunol. 2004; 114: 1010-20.

Cox JE, Cheng TL. Egg-based Vaccines. Pediatrics in Review. 2006;27:118-119.

Centers for Disease Control and Prevention. Assessed December 12, 2007.

DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.