Real-World Evaluation of Allergic Reactions to Two Measles, Mumps, and Rubella Vaccine Formulations in Children with Egg and/or Cow's Milk Allergy.

Abstract

Introduction: Cow's milk allergy (CMA) and egg allergy (EA) are among the most common food allergies in childhood. Although measles, mumps, and rubella (MMR) vaccination is generally considered safe in food-allergic children, uncertainty persists among clinicians and families regarding the clinical relevance of residual food proteins in different MMR vaccine formulations. This study aimed to evaluate adverse reactions following administration of two different MMR vaccines in children with confirmed CMA and/or EA and to explore implications for safe immunization practices.

Methods: We retrospectively analyzed 140 children with diagnosed CMA and/or EA who received the MMR vaccine at our pediatric allergy clinic between September 2022 and May 2025. Demographic data, allergen-specific IgE levels, skin prick test results, MMR vaccine type and postvaccination reactions, were recorded. Two formulations were used: the Serum Institute of India vaccine (α-lactalbumin-containing) and Priorix® (α-lactalbumin-free).

Results: Among the patients, EA was observed in 60%, CMA in 17.1%, and both in 22.9%. Atopic dermatitis was present in 56.4%, urticaria in 31.4%, and a history of anaphylaxis in 12.1%. Overall, 57.9% (n = 81) received the α-lactalbumin-containing vaccine, while 42.1% (n = 59) received Priorix®. Only 1 (0.7%) patient experienced anaphylaxis after vaccination with the α-lactalbumin-containing formulation. No other serious adverse reactions were recorded.

Conclusion: MMR vaccination was generally well tolerated in children with egg and/or CMA. While rare immediate reactions may occur with vaccines containing milk-derived proteins, these findings support continued adherence to current vaccination recommendations, with awareness of vaccine composition and appropriate vaccination settings rather than vaccine avoidance.