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

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

Esra Yucel, MD, assistant professor in the division of pediatrics, department of pediatric allergy and immunology at Istanbul Faculty of Medicine of Istanbul University, and colleagues treated these patients at their pediatric outpatient clinic, according to the findings from a clinical letter published in Pediatric Allergy and Immunology.

The first case involved a boy aged 4 years 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) at 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 providers treated him with intramuscular epinephrine and referred him to the outpatient clinic for further evaluation.

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

In the second case, a girl aged 1 year with a history of anaphylaxis following exposure to cow’s milk, hen’s egg and chicken meat developed anaphylaxis after MMR vaccination with the Tresivac brand of 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 providers immediately administered intramuscular adrenaline, and all symptoms then improved.

Analysis revealed that the vaccine used in these cases as well as in previous case reports of anaphylaxis after the measles vaccine were from the same manufacturer. The providers then decided to use another brand of MMR vaccine that does not include any milk components when vaccinating children with severe cow’s milk allergy.

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

“Health care professionals should be aware of the fact that in patients with IgE-mediated

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