This is a very difficult case, so I reached out to Dr. John Kelso.
Response from Dr. Kelso:
Cases of SJS following vaccination are exceedingly rare. A recent publication reviewed these cases. (Chahal D, Aleshin M, Turegano M, et al. Vaccine-induced toxic epidermal necrolysis: A case and systematic review. Dermatology Online Journal 2018;24. pii: 13030/qt7qn5268s.)
The vaccines are typically only implicated by the temporal association as opposed to any test to prove the vaccine was causal. Similarly, there is no test to predict the likelihood of a recurrence with MMR or other vaccines. Her recent tolerance of Td or Tdap demonstrates that she can receive some vaccines.
In addition to the immunizing agents, MMR contains:
• Sorbitol, 14.5 mg
• Sodium phosphate, amt not specified
• Sucrose, 1.9 mg
• Sodium chloride, amt not specified
• Hydrolyzed gelatin, 14.5 mg
• Recombinant human albumin, ≤0.3 mg
• Fetal bovine serum, <1 ppm
• Other buffer and media ingredients, amt not specified
• Neomycin, ~25 mcg
The only excipient implicated consistently in any sort of immune reaction is the gelatin which has caused IgE mediated reactions (which this clearly was not) and possibly delayed type hypersensitivity reactions (which conceivably this was). Thus, in addition to the MMR, there could be some possible concern regarding other gelatin containing vaccines, although this is theoretical.
Vaccine and Gelatin Content
Influenza (FluMist, MedImmune Vaccines) - 2 mg per 0.2 ml dose
Measles, Mumps, Rubella (MMRII, Merck) - 14.5 mg per 0.5 ml dose
Measles, Mumps, Rubella, Varicella (ProQuad, Merck) - 11 mg per 0.5 ml dose
Rabies (RabAvert, Novartis) - 12 mg per 1.0 ml dose
Typhoid Vaccine Live Oral Ty21a (Vivotif, Crucell) - capsule
Varicella (VARIVAX, Merck) - 12.5 mg per 0.5 ml dose
Yellow Fever (YF-VAX, Sanofi Pasteur) - 7.5 mg per 0.5 ml dose
Zoster (ZOSTAVAX, Merck) - 15.58 mg per 0.65 ml dose
Whatever risk there is of vaccination must be weighed against the risk of remaining unvaccinated. I agree with your assessment that it would be appropriate to check measles mumps and rubella titers and if protective forgo any additional MMR vaccination but to present this information to the patient and propose proceeding with other required vaccines with the possible exception of those containing gelatin.
Respectfully submitted, Jeffrey G Demain, MD