A clinical analysis of gelatin allergy and determination of its causal relationship to the previous administration of gelatin-containing acellular pertussis vaccine combined with diphtheria and tetanus toxoids

Background: The number of patients with allergic reactions after administration of gelatin-containing live vaccines is increasingly reported in Japan. These allergic reactions appear to be caused by gelatin allergy. It is still unknown how the patients mere sensitized to gelatin. Objective: To determine the incidence of gelatin allergy and to identify contributing factors to gelatin allergy, me investigated the following clinical aspects: the development of IgE antibodies to gelatin and the relationship of the patients' past history of acellular pertussis vaccine combined with diphtheria and tetanus toroid (DTaP) to the development of gelatin allergy. Methods: We evaluated 366 patient reports, submitted from 1994 to 1997, of adverse reactions after immunization with monovalent measles, mumps, and rubella vaccines containing 0.2% gelatin as stabilizer. On the basis of physician reports, the patients were categorized as to the nature of the adverse reaction. We determined the presence of IgE antibodies to gelatin and obtained past immunization history. Results: The 366 reported patients were categorized as follows: 34 with anaphylaxis, 76 with urticaria, 215 with nonurticarial generalized eruption, and 41 with local reactions only. In 206 patients from whom serum was available, IgE antibodies to gelatin were detected in 25 of 27 (93%) with anaphylaxis, 27 of 48 (56%) with urticaria, and 8 of 90 (9%) with a generalized eruption. None of a group of 41 patients with only local reactions at the injected site and none of a control group of 29 subjects with no adverse reaction had such antibodies. Among 202 patients for whom prior vaccine information was available, all had received DTaP vaccines. Among those for whom the prior DTaP vaccine could be determined to contain gelatin or be free of gelatin, 155 of 158 (98%) subjects had received gelatin-containing DTaP vaccines. This rate is higher than mould be expected on the basis of the market share of gelatin-containing (vs gelatin-free) DTaP vaccines (75%). Furthermore, before 1993, when a trivalent measles, mumps, and rubella vaccine (with the same 0.2% gelatin content as the monovalent vaccines) was used and administered before DTaP vaccination, no reports of anaphylaxis to the measles, mumps, and rubella vaccine were received. Conclusion: Most anaphylactic reactions and some urticarial reactions to gelatin-containing measles, mumps, and rubella monovalent vaccines are associated with IgE-mediated gelatin allergy. DTaP immunization histories suggest that the gelatin-containing DTaP vaccine may have a causal relationship to the development of this gelatin allergy.