This case was reported in a literature article and described the occurrence of anaphylaxis in a 4-year-old male subject who was vaccinated with DTAP vaccine (manufacturer unspecified). The subject's medical history included asthma and proctocolitis. Concurrent medical conditions included allergy to cow's milk. On an unspecified date, the subject received an unspecified dose of DTAP vaccine (administration site and route unknown, batch number not provided). 10 minutes after vaccination with DTAP vaccine, the subject experienced anaphylaxis, respiratory distress and diffuse hives. This case was assessed as medically serious by GSK. Milk specific IgE level was 82.9 kIU/L. The subject was treated with diphenhydramine and steroid. At the time of reporting, the outcome of the events was unspecified. This case has been linked to 7 other cases of anaphylaxis after vaccination with diphtheria, tetanus and pertussis vaccines in the same literature article: B0733765A, B0733767A, B0733779A, B0733780A, B0733781A and B0733783A. Summary of the literature article: Immediate-type hypersensitivity to cow's milk affects approximately 1% to 2% of young children, can persist, and can be fatal. Vaccines against tetanus, diphtheria, and pertussis are routinely given to children in multiple doses throughout childhood. Anaphylactic reactions to these vaccines are rare and are generally attributed to the vaccine toxoids. The US national Vaccine Adverse Events Reporting System lists 39 anaphylactic reactions to DTaP, DTP, or Tdap vaccines for subject's aged 0 to 17 years from 2007-2010. In this period, the authors observed 8 children in their single center with a history of anaphylactic reactions to booster doses of these vaccines. The authors noted that these vaccines are labeled as being processed in medium containing casamino acids (derived from cow's milk), raising the concern that residual casein in the vaccines might have triggered these reactions. We are not aware of prior reports linking milk contamination to anaphylaxis from these vaccines. To investigate this possibility, the authors reviewed the medical history of the affected children and tested 8 lots of the vaccines for residual casein. These subjects were selected based on reports of anaphylactic reactions to the vaccines and not because of a history of milk allergy. Each patient had symptoms consistent with anaphylaxis within 1 hour of administration of the vaccine. Six of the subjects had prior acute allergic reactions to cow's milk, including severe reactions in 5 subjects and reactions to trace exposures in 4 subjects. One subject was given a diagnosis of milk allergy based on serologic testing performed to evaluate atopic dermatitis, and another was given a diagnosis based on serologic testing to evaluate proctocolitis. Each of the subject's had an increased milk-specific IgE level documented within 2 years of the reaction to the vaccine. Although milk-specific IgE levels do not necessarily correlate with severity, the recorded levels are far above those that typically correlate with reactivity. In summary, the authors identified 8 patients with severe milk allergy who reaction with anaphylaxis to Tdap or DTaP vaccines, which are processed in a broth derived from casein. They identified casein in 8 lots of the vaccines, raising the concern that residual casein in the vaccines might result in reactions for highly sensitive patients with milk allergy. Most children with cow's milk allergy receive these vaccines without incident, but the subjects they identified have very severe milk allergy, very high milk-specific IgE levels, and, for 4 of them, past reactions to trace milk contamination. These children tolerated their initial vaccinations but reacted to booster doses. This observational is most likely explained by increasing milk sensitivity of the children as they aged, as reflected in the personal histories of several of the children. In conclusion, our novel observation raises a concern regarding booster vaccination of children with high levels of milk allergy with Tdap and DTaP. Although the children they identified appear by history and testing to be exquisitely allergic to milk, they cannot accurately define a high-risk group based on this case series. They recommended continuing the standard practice for DPT vaccination in all children, but advised caution when administering booster doses in highly sensitive milk-allergic children.