Background on the Carey Study
Numerous studies have shown that latex condoms are a highly effective barrier to viruses, including HIV, the virus that causes AIDS, and the much-smaller hepatitis B virus. However, the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) continue to receive inquiries about a laboratory study of latex condoms, commonly called "the Carey study." [Carey, R.F., Herman, W.A., Retta, S.M., Rinaldi, J.E., Herman, B.A., and Athey, T.W. Effectiveness of Latex Condoms As a Barrier to Human Immunodeficiency Virus-sized Particles Under Conditions of Simulated Use. Sexually Transmitted Diseases, July-August 1992, pages 230-234.] This study examined the effectiveness of latex condoms as a barrier to particles the size of HIV, the virus that causes AIDS.
In the Carey study, latex condoms were tested under laboratory conditions that matched some circumstances of actual use: the condoms' size and shape were standard and test particles inside the condoms were the size of HIV. But other conditions were deliberately exaggerated: the particle concentration was much higher than the concentration of HIV in semen, the test itself lasted 30 minutes, the pressure inside the condom was always at the maximum expected during use (as opposed to intermittently at the maximum), and the fluid was 14 times less viscous (thinner, and therefore easier to pass) than semen. These exaggerated conditions were used to push condoms toward failure, to find out the limits of their performance.
The results were clear: The condoms in this study would reduce exposure to HIV by at least 10,000 times. Even under these extreme laboratory-created conditions, only 1 of the 89 condoms tested leaked enough to allow passage of a small amount of virus during actual use -- and even that worst-case condom would have still reduced exposure to HIV by more than 1,000 times over not using a condom at all.
These laboratory tests have been misinterpreted as proving condoms don't work as a protective device against HIV transmission. The truth is, the tests proved that condoms work exceptionally well.