The nurse tells the students she is giving them a "vaccination" that will stop the "virus." As was mentioned, syphilis is caused by a bacterium known as Treponema pallidum. In addition, there is no vaccination for syphilis; the intramuscular injection that the nurse was giving the students is Penicillin G, an antibiotic.
When the students are being treated, the nurse injects them in their arms. Syphilis injections are supposed to be administered in the buttock.
This movie stated that syphilis is caused by a virus. Syphilis is actually a bacterium.