Anaphylaxis Complicating Routine Childhood Immunization: Hemophilus Influenza b Conjugated Vaccine

Increasing numbers of vaccines are being introduced into the infant and childhood immunization schedules. Immediate hypersensitivity reactions to include anaphylaxis can occur during the immunization visit. Determining the cause of a vaccine-associated immediate hypersensitivity reaction may require multiple specific skin test and challenge procedures. We report the case of a 4-month-old Caucasian male who developed an urticarial rash within 10 minutes of receiving his 4-month immunizations, diphtheria-tetanus-acellular pertussis (DTaP), inactivated polio (IPV), and the diphtheria mutant protein (CRM¹⁹⁷) conjugated Hemophilus influenzae type b (HbOC). The child was referred for an allergy-immunology consultation in order to determine the cause of the reaction and a future vaccine management strategy. Negative prick skin tests were obtained with full-strength vaccine and subsequent dose challenges with DTaP and IPV vaccines were tolerated without reaction. Prick skin testing with full-strength HbOC was negative, but dose challenge with 0.05 mL resulted in an anaphylactic reaction within 10 minutes of the first challenge dose. The reaction included generalized hives, nasal congestion and diffuse wheezing. Subsequent intradermal skin testing with four different Hemophilus influenzae type b (Hib) vaccines at 1:100 dilution revealed isolated skin test reactivity to HbOC but not the other protein conjugated Hib vaccines. Skin testing with CRM¹⁹⁷ alone (the protein conjugate in HbOC) was positive, confirming the source of the reaction. The patient tolerated subsequent Hib immunization with a CRM-free preparation without complications. Our case report suggests that the mutant diphtheria protein CRM¹⁹⁷ may be an allergenic protein in some patients who develop anaphylaxis to the HbOC vaccine. The availability of vaccines with different protein conjugates provides an alternative vaccination strategy for those patients with specific sensitization. The question of cross-reactions and risk for anaphylaxis with other vaccines containing the CRM¹⁹⁷ remains to be determined. The new pneumococcal vaccine (Prevnar™) contains CRM¹⁹⁷. (Pediatr Asthma Allergy Immunol 2000;14[4]:316-321.)