D1.302 - Allergic Reactions Following Measles-Mumps-Rubella Vaccination in Children with Food Allergy: A Single Center Experience

A history of allergic reactions may lead to vaccine hesitancy and referral to tertiary allergy clinics, although confirmed vaccine-related allergic reactions are generally rare. Some MMR formulations have been reported to contain alfa-laktalbumin raising concern in children with cow’s milk allergy. We aimed to evaluate the frequency and clinical characteristics of reactions after MMR vaccination in children referred for suspected or diagnosed food allergy.

Children who received MMR vaccination at the Pediatric Immunology and Allergy Clinic, Ankara Training and Research Hospital, between January 1, 2020 and January 1, 2026 were retrospectively reviewed. Demographic, clinical and laboratory data were extracted from medical records.

A total of 204 children were included (59,8% male, n=122), with a median age at presentation of 6,1 months (IQR 5-9). The most common presenting complaint was eczema (40,7%), followed by non-specific erythema (31,9%) and bloody stools (7,8%). Food allergy was present in 168 (82,4%) children, egg allergy in 71,6% (n=146) and cow’s milk allergy in 27,5% (n=56). The most frequent comorbid allergic condition was atopic dermatitis (59,8%).

Overall, 250 MMR doses were administered. Five children experienced an allergic reaction (2.4% per patient; 2% per administered dose): four after the first dose and one after the second dose. Reactions comprised anaphylaxis (n=2), urticaria (n=1), and maculopapular rash (n=2); three occurred within 30 minutes and two at approximately 2 hours post-vaccination. All reactions were associated with vaccines recorded as belonging to the α-lactalbumin–containing group.

Allergic reactions following MMR vaccination were uncommon among children with food allergy. Our findings support that MMR can be administered safely under appropriate conditions. The clustering of reactions with specific formulations underscores the need for further studies with clearly defined denominators to clarify the potential role of vaccine components/excipients, including milk-derived ingredients reported in some preparations.