If they are used and stored correctly, rubber condoms are efficient mean for prevention of sexually transmitted diseases including HIV as well as from unwanted pregnancy.
Many studies have shown that risk of infection with sexually transmitted diseases, depending from frequency of their use is balancing between 0-25%. Lately, it’s been talked that condoms don’t save you from HIV/AIDS. As a reason is mentioned fact that latex has micro-pores. As you know, you can get infected with HIV contacting with body fluids of infected person (blood, sperm and vaginal discharges).
So if condom is hermetic then it doesn’t let through not only water but also HIV virus. Though, “hermetic” doesn’t mean that there can’t be micro-pores in latex, factor good enough is that it’s not letting through liquids. As an example we can mention the simple umbrella – it has material which doesn’t let water get through although it has pores. Another example is gauze/cotton-wool mouth bandage which are used to prevent infection with flu (it’s also infection caused by virus). Pores of this bandage you can see without a microscope.
All these are theoretical deliberations. To judge particularly – are condoms preventing from infection with HIV or not, it’s necessary to do a study – to survey the sexual partners, where one of them is HIV positive. Such a study was made in Europe. It was 22 month long and 124 couples participated, where one of the partners were HIV positive and these couples always used condoms at their contacts. In the same time, there were surveyed couples where one of the partners was also HIV positive but used condoms irregularly. At the end of the study it turned out that approximately 10% of partners were infected with HIV. So we can say with assurance, that regularly and properly using condom at sexual contacts will save you from infecting with HIV virus.
A little bit different it is with sexually transmitted diseases, which are possible to transfer from infected person to healthy one. One of the main reasons for getting infected with sexually transmitted diseases at sexual contact if there are used condom is it’s improper use (breaking, infecting while taking it off) and transfer of infection with hands (during foreplay, transferring infection to own genitals).