BALTIMORE — A new allergy risk to a common ingredient has been identified in a recent case study that has implications for vaccination. Gelatin, often found in lunchmeats, jellies, and gummy candies, is also used in vaccines, and allergy — though rare — can trigger anaphylaxis.
An allergy to egg is no longer considered a risk of flu vaccination, but investigators presenting here at the American College of Allergy, Asthma & Immunology (ACAAI) 2013 Annual Scientific Meeting warned that gelatin allergy can be a problem.
It is rare, and the first case reports were published in the mid-1900s, Stephanie Albin, MD, from the Jaffe Food Allergy Institute at Mount Sinai in New York, New York, told Medscape Medical News. However, it can present significant issues because many vaccines — and foods — contain gelatin.
Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from cow, pig, and fish, she explained. Patients with gelatin allergy do not react to meat because gelatin is derived from tendons and bones rather than the flesh. And gelatin in vaccines is more likely to cause an allergic reaction because it is concentrated, purified, and processed and has direct access to the immune system through injection.
Vaccines that contain gelatin include those against influenza; measles, mumps, and rubella (MMR); varicella; yellow fever; zoster; rabies; Japanese encephalitis; and diphtheria, tetanus, and pertussis (DTaP).
The case report involved a 4-year-old boy with a presumed egg allergy who was avoiding unbaked egg upon developing a perioral rash after eating meringue icing.
"He had received the influenza vaccine in the past without any issue, but that year he developed diffuse hives, watery eyes, sneezing, and vomiting within 15 minutes of receiving the immunization," Dr. Albin reported.
A complete history of the patient's food reactions revealed that he had previously developed a watery mouth, abdominal pain, and weakness after eating gummy candies, gummy vitamins, and marshmallows. The patient was also avoiding peanuts, tree nuts, fish, and shellfish because of a family history of food allergy.
Skin-prick testing showed a 4-mm wheal and 21-mm flare with commercial egg extract, as well as a 13-mm wheal and 33-mm flare with fresh gelatin. Serum testing showed an IgE level of 4.76 kIU/L for egg white and 0.39 kIU/L for bovine gelatin. Positive IgE levels were also noted for salmon.
The patient was offered an oral food challenge to salmon with the idea that salmon-derived gelatin might be safe, but the family declined and preferred to defer any immunization with gelatin-containing vaccines, Dr. Albin said.
There are gelatin-free alternatives to some vaccines, including those against influenza and DTaP, but not to others, including those against zoster and MMR.
The patient was instructed to avoid egg, salmon, and gelatin and to introduce peanut, tree nuts, and shellfish at home one at a time. A prescription was given for an epinephrine autoinjector and an emergency action plan discussed.
The patient's previous influenza immunizations may have been administered before clinical sensitization, senior author Anna Nowak-Wegrzyn, MD, from the Icahn School of Medicine at Mount Sinai, explained to Medscape Medical News.
"There is always a sensitization period during which allergy develops. It may depend on the patient's immune system and on the amount of gelatin in the vaccines that is highly variable," she said.
The index of suspicion for gelatin allergy depends on the allergic reaction, said Dr. Albin. "If a patient had anaphylaxis after vaccination, you should consider gelatin allergy. If a patient had a large local reaction after vaccination, it is less likely to be gelatin allergy."
It's very uncommon to be allergic to gelatin, but if you see a reaction to the influenza vaccine it is probably gelatin and not egg allergy, confirmed Jay Portnoy, MD, chair of the abstract committee for ACAAI 2013.
A recent update from the American Academy of Allergy, Asthma & Immunology and ACAAI Joint Task Force on Practice Parameters say that patients with any severity of egg allergy can safely receive the influenza vaccine with no special precautions (Ann Allergy Asthma Immunol. 2013;111:301-302).
Many physicians remain unaware of this update, and even current recommendations from the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices do not reflect this information, Dr. Portnoy told Medscape Medical News.
"Some allergists are aware of this and some are not, and I can guarantee that none of the primary care doctors are aware because they send me their egg-allergic patients and I just give them the flu shot. I see a lot of them," he said.
A new warning may end up replacing the previous egg allergy precautions after a case report of pediatric anaphylaxis to the influenza vaccine was traced back to gelatin allergy.
The study authors have disclosed no relevant financial relationships. Dr. Portnoy reports work with Sanofi, Thermo Fisher Scientific, and Mylan.
American College of Allergy, Asthma & Immunology (ACAAI) 2013 Annual Scientific Meeting. Abstract P104. Presented November 9, 2013.
Medscape Medical News © 2013 WebMD, LLC
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Cite this: Flu Vaccine Allergy May Be Attributed to Gelatin, Not Egg - Medscape - Nov 21, 2013.