Systemic allergic reactions to gelatin included in vaccines as a stabilizer

Most of the children who showed systemic immediate-type reactions, including anaphylactic shock, to measles, mumps, rubella, and varicella vaccines had IgE antibodies to gelatin; thus we suspected that the allergic symptoms are caused by gelatin antigen, which is usually included in these live-virus vaccines as a stabilizer. We hypothesized that the anti-gelatin IgE is elicited by immunization with DTaP (diphtheria-tetanus-acellular pertussis) vaccines, which contained a small amount of gelatin as a spillover protein after purification of pertussis toxin. To test this hypothesis, we conducted a case-control study to determine whether children with anti-gelatin IgE had received gelatin-containing DTaP vaccines, and it was indeed found that all such children in the study had immunization histories that included the gelatin-containing DTaP vaccines. Based on these findings, the vaccine manufacturers had removed gelatin from all the DTaP and live-virus vaccines produced in Japan by 2000.