for people who keep getting infections, taking antibiotics for a long time is helpful. drugs frequently used include nitrofurantoin and trimethoprim/sulfamethoxazole. if infections are related to sexual intercourse, some women find it useful to taking antibiotics after sex. in post-menopausal women, using topical vaginal estrogen (a hormone applied to the skin of the vaginal) has been found to reduce getting a uti. unlike topical creams, the use of vaginal estrogen from pessaries (medical devices put in the vagina is not as useful as low-dose antibiotics. a number of vaccines are being developed (as of 2011).