Allergic reactions to measles-mumps-rubella vaccination

Objective. Immunization of egg-allergic children against measles, mumps, an d rubella (MMR) is often deferred or even denied, although the safety of th is vaccination has been clearly shown. Moreover, the majority of severe all ergic reactions have occurred in egg-tolerant vaccinees. Other allergenic v accine components have been sought, and gelatin has been suggested as one c ause of allergic adverse events. The aim of this study was to further chara cterize the actual allergenic vaccine components. Methods. Serum samples from 36 recipients of MMR vaccine with anaphylaxis, urticaria with or without angioedema, asthmatic symptoms, or Henoch-Schonle in purpura were analyzed by CAP System radioallergosorbent test (RAST) and immunospot methods to detect the allergenic vaccine component. To evaluate the correspondence between the findings in the CAP System RAST or the immun ospot and clinical symptoms, histories of allergies and present hypersensit ivity symptoms were assessed. Results. Of the 36 participants, 10 were demonstrated to be allergic to gel atin. Seven of them had persistent allergic symptoms, possibly attributable to foods containing gelatin or cross-reactive allergens. The results of th e immunospot suggested concomitant allergy to gelatin and egg, chicken, and feathers, as well as cow's milk, or they reflected allergen cross-reactivi ty. Conclusions. Although severe allergic adverse events attributable to MMR va ccination are extremely rare, all serious allergic reactions should be furt her assessed to detect the likely causative vaccine component, including ge latin. The current recommendation for immunization of egg-allergic persons according to standard MMR vaccination schedules is reinforced.