Thank you for your recent inquiry.
I wish that there was an answer to your question, but I am afraid the dilemma is one for which there is no evidence-based response. There is no test that will tell you whether or not a drug or vaccine was responsible for a case of erythema multiforme. Normally if there was strong suspicion that a drug produced this syndrome, it should of course be avoided in the future. However, when a drug may be essential for the patient’s welfare (as in the case of influenza vaccine), the decision to readminister the drug is one based purely on a personal assessment of risk/benefit ratio, and there is no test that you can perform to even give you a better sense of the statistical probability of a recurrence.
Therefore, unfortunately, in this case, you would simply discuss the issues with the parents and help them decide on whether or not the potential benefit of administration outweighs the potential risk of a recurrence.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.