Hi, I understand your concern. Bactrim is known to cause Steven Johnson syndrome and it also causes many other skin reactions. Some influenza vaccines also contain antibiotics, especially sulfa group of antibiotics, the same in Bactrim. It is unlikely that the vaccine caused steven johnson in your case. However, to be safe, just ask your doctor to check the content label on that vaccine bottle to see if it contains sulfa drugs. If it does, try another brand that is free of sulfa and you would be all right. Also, next time you get a pimple try some topical medicines like benzyl peroxide gel application on the pimple rather than oral medicines. Take care and thanks for using HCM.