oh yes tetanus. From what I know, tetanus is caused by the organism Clostridium tetani. This bug causes muscle rigidity. Based on what's written on the books, serotonin syndrome and neuroleptic malignant syndrome's rigidness are caused by the increase of calcium release at the muscles. Tetanus vaccine would probably stop the tetanus toxins released by the Clostridium and not stop the calcium release caused by anti-psychotics or SSRIs. Thanks for mentioning though, quite a good question. I've never thought of this before.