Despite this, the use and promotion of condoms continue to be targets for controversy and criticism, and sexual abstinence and monogamy are often promoted as superior alternatives.
Laboratory studies and product testing have shown that reputable condoms tested in the laboratory are completely impermeable to micro-organisms as small as viruses.However, the same studies show that condoms come off the penis altogether 3 to 5% of the time but may slip down (but not off) up to 13% of the time.Another kind of study is to conduct a prospective cohort study, looking at differences in HIV incidence between two groups of people according to their usage of condoms.This cannot be a randomised controlled study, but participants’ HIV and STI incidence can be related to their condom use either at baseline or preferably (because behaviours change over time) by means of regular questionnaires and monitoring.The next problem is deciding what kind of study provides truly reliable evidence.
It would be unethical to mount a randomised trial of condom use because the control group would have to stop using them altogether.
These can be done in individuals whose characteristics are known and can be controlled for, and if the relationship truly is monogamous then infections by acute STIs and from outsiders can be ruled out.
One disadvantage is that condom use in long-term relationships, even in serodiscordant couples, is relatively rare.
The main findings of studies we look at in more detail below are as follows: These degrees of protection may be lower than some readers expect, and rates of 98% reliability are still sometimes quoted for condoms.
These are based upon observations of their use in contraception: studies have shown that 98% of women relying on condoms as their sole form of contraception remain pregnancy free if condoms are used perfectly, meaning that they are used consistently and correctly at every act of sexual intercourse.
For these reasons, HIV transmission within long-term serodiscordant relationships, especially heterosexual ones, may be rarer than it is between casual sex partners.