I’ve posted a few times on condoms, most recently talking about porn and why OSHA should insist condoms be used to protect adult film performers. I follow these posts with lots of randoms tweets about condoms. Inevitably, after each post or tweet someone is flumoxed by the statistic that condoms reduce HIV transmission by 85%.
“Only 85%?” They say. “Yikes.”
Some even ask for references and evidence, and you know nothing gets me all worked up (in a good way, or course) than the quest for truth!
Fortunately, a Cochrane Review was published this year (by Weller and Davis-Beaty) reviewing the data on Condom effectiveness in reducing heterosexual HIV transmission. So that’s my source, the latest Cochrane review (2011 in case you are reading this post sometime in the future). The last Cochrane review on the subject was 2004.
Side bar for those who don’t know about Cochrane reviews. In short, it’s a review of the medical literature only considering the highest quality evidenced based articles. Some Cochrane reviews suffer because there are insufficient numbers of high enough quality studies to use (there were enough studies for the condom review). Cochrane reviews are also focused on homogeneous populations. Many people draw conclusions by comparing studies without realizing that they are looking at slightly different groups of people or slightly different interventions, but that is comparing apples or oranges and just doesn’t fly. The groups and the interventions need to be similar. To give you an idea of how many studies are discarded, the Cochrane review on condoms started with 4,709 studies. Only 14 were included in the final analysis.
Because it isn’t ethical to do a study on how well condoms work at preventing HIV (you can’t intentionally tell someone who has an HIV positive partner to avoid condoms!!), the data comes from following people who have to decided to always use condoms and people who never use condoms. These are called cohort studies.
Condoms studies look at either “always” user, “sometimes” users, and “never” users (in case you are wondering, “always” is the preferred method). The Cochrane review looked at studies of “always” users, meaning for every act of vaginal penetration, and compared them with “never” users.
Based on the high quality studies in the Cochrane review, if 100 people have sex on a regular basis with a partner who is HIV positive, 5.75 will become HIV positive themselves after a year. Factors such as receptive anal intercourse and not taking antiretroviral medications will increase that risk (not covered in the Cochrane review, but well studied elsewhere).
People who use condoms all the time reduce their risk of getting HIV by 80% (so slightly less than I had been quoting), however based on the studies condom effectiveness at preventing HIV could range anywhere from 35% to 94%.
So condoms are definitely effective, but they are not 100%.
So…what does this mean?
Think of condoms like a seatbelt, they are only one safety tool and shouldn’t preclude you from other safety measures, such as knowing your partner, being faithful, and not engaging in casual sex.
The fact that condoms are not 100% effective at preventing HIV transmission also supports other complementary strategies such as being faithful to your partner, antiretroviral medication, adult circumcision, and control of herpes and bacterial vaginosis. Since no single intervention is 100% effective, disease eradication will probably take all of them
Always use a condom, but understand they are not 100%. Not even when you use them always.
That message should be printed over the entrance to every bar…