Adverse reactions to vaccines incorporate both allergic and non-allergic reactions. Millions of routine childhood vaccinations are given every year in the UK. It is reassuring therefore that allergic vaccine-induced reactions are increasingly rare events. 

The following foods/antibiotics are present in small amounts in routine childhood vaccines. 

Egg

• The MMR vaccine remains the best form of protection against measles, mumps and rubella infection, yet the uptake of the MMR vaccine is still below targets. As a result children are being exposed to unnecessary suffering and occasional serious consequences as a result of developing these infections. 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, safely tolerate the MMR vaccine. Therefore, the Paediatric Allergy Group of the BSACI, the American Academy of Pediatrics, and other Paediatric Groups in the World, recommend that children with egg allergy can safely be given the MMR vaccine without any special measures being taken. Advice is also available from Dr Du Toit with respect to the lack of rationale for the administration of single MMR vaccinations. One reason for the low uptake of MMR in the UK has been the mistaken belief that children with egg allergy cannot be given MMR. The Paediatric Allergy Group of the British Society for Allergy and Clinical Immunology has reviewed the evidence and, in fact, there is no evidence that egg allergy is a problem with using MMR. The modern MMR vaccine is grown on cultured – embryo chick fibroblasts and is therefore generally free of hen’s egg protein. When traces of hen’s egg protein are found, the protein is highly processed and the concentrations are too low to represent a risk of triggering an allergic reaction. Therefore the Paediatric Allergy Group recommends that MMR can be administered safely to all egg-allergic children in primary care, without any special precautions. The BSACI Paediatric Allergy Group states that “Egg-allergic children who have not had problems with other vaccinations can safely be given MMR in primary care. Specialist assessment is only required if any previous vaccinations have resulted in a severe allergic reaction (including any breathing problems or collapse)”.

• 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. The Yellow Fever Vaccine can however only be administered by certified vaccine centres, many of which do not have expert allergy experience. Dr Du Toit will be able to advise on these issues.

Gelatin

• Gelatin (bovine or porcine derived), 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 an allergist.

Antibiotics 

• The most commonly used class of Antibiotic in Vaccines are the 'aminoglycosides' such as neomycin or gentamycin. This class of antibiotic is generally very safe with only very few antibiotic allergic children being sensitive to this antibiotic. Allergy testing to this antibiotic is available.

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 an allergist.

UK Allergy Schedule