Consistently used condoms provide significant protection against HIV, pregnancy and sexually transmitted infections (STIs).
The degree of protection they offer against HIV and STIs is significantly better than any other single prevention method, taken in isolation, other than sexual abstinence or complete mutual monogamy between two people who have tested negative for HIV.
However, because they are not always used correctly even if they are used consistently, studies have found efficacy rates of 85 to 87% when young women use condoms as their sole form of contraception.
Condoms are, however, the only method on that list that has been shown to protect against STIs as well as pregnancy.
Studies of condom efficacy have therefore largely contrasted HIV and STI incidence or prevalence in people who claim 100% consistent use against people who use them inconsistently or not at all.