While condoms are highly effective in reducing the transmission of many STIs, they are not 100% foolproof. They are most effective against infections spread through bodily fluids, such as HIV and gonorrhea. However, they may be less effective against STIs transmitted through skin-to-skin contact, such as HPV and herpes simplex virus (HSV). Proper and consistent use of condoms can significantly lower the risk of infection, but it does not eliminate it entirely.