‘Hidden allergen’ in MMR vaccine may cause anaphylaxis in children with cow’s milk allergy


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Two children with severe cow’s milk allergy developed anaphylactic reactions after receiving doses of a measles, mumps and rubella or MMR vaccine containing the alpha-lactoglobulin component of milk, researchers reported.

Esra YucelMD, assistant professor in the Department of Pediatrics, Department of Pediatric Allergy and Immunology at Istanbul University’s Faculty of Medicine, and colleagues treated these patients at their pediatric outpatient clinic, according to the findings of a clinical letter published in Pediatric Allergy and Immunology


boy is vaccinated


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The first case involved a 4-year-old boy diagnosed with cow’s milk allergy and recurrent anaphylaxis due to accidental exposure to cow’s milk, who received an MMR vaccination (Tresivac, Serum Institute of India) in the clinic according to the routine national immunization schedule.

Within 10 minutes, the patient developed restlessness, constant and hoarse crying, difficulty breathing, drooling, nasal congestion and discharge, and angioedema of the lips. Also, his blood pressure was 72 mm Hg/46 mm Hg. The caregivers treated him with intramuscular epinephrine and referred him to the outpatient clinic for further examination.

The reaction was consistent with the patient’s medical history and lab findings, so the suppliers considered the hydrolyzed lactalbumin in the vaccine to be the cause of the anaphylaxis without the need for a whole vaccine skin test.

In the second case, a 1-year-old girl with a history of anaphylaxis after exposure to cow’s milk, chicken egg and chicken meat developed anaphylaxis after MMR vaccination with Tresivac vaccine.

Within 5 minutes of receiving the dose, the patient had difficulty breathing, hoarse crying and a cutis-like appearance on her body, with a blood pressure of 55 mm Hg/30 mm Hg. The caregivers immediately administered intramuscular adrenaline and all symptoms improved.

Analysis showed that the vaccine used in these cases and in previous cases of post-measles anaphylaxis was from the same manufacturer. The providers then decided to use a different brand of MMR vaccine that does not contain milk components when vaccinating children with severe cow’s milk allergy.

The authors noted that vaccine hesitancy is a major health problem both in local communities and around the world, and encouraged vaccine manufacturers to exercise maximum caution and use standard vaccine components to produce safer vaccines.

“Healthcare professionals should be aware that in patients with IgE-mediated

food allergies, drugs and vaccines may be an accidental way of encountering hidden allergens,” the researchers wrote. “Especially in cases of severe food allergy, the patients’ medical history, vaccine contents and package inserts should be carefully evaluated before vaccination.”

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