If you don't mind taking a bunch of pills you can get nearly 100% protection against getting HIV and about 60%-75% protection against Chlamydia, gonorrhea, syphilis. Also throw in some acyclovir or similar for herpes protection. Personally, I would just use a condom. I know some will say they can't enjoy with a condom but it seems like a lot of stress on your body, kidneys, to take all these pills just to have condom free sex. As always, to each their own.