STDs Expert Forum
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The STD Forum is intended only for questions and support pertaining to sexually transmitted diseases other than HIV/AIDS, including chlamydia, gonorrhea, syphilis, human papillomavirus, genital warts, trichomonas, other vaginal infections, nongonoccal urethritis (NGU), cervicitis, molluscum contagiosum, chancroid, and pelvic inflammatory disease (PID). All questions will be answered by H. Hunter Handsfield, M.D. or Edward W Hook, MD.

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Hello, I have a question about condoms.
When I read and hear about condoms I find that the opinion about their effectivness against STD varies a lot.
Some sais there is no risk of getting a STD with a proper used condom, some sais it goves "good protection against STD´s", some sais "it's not 100%" and some sais "it only gives minor protection against some STD´s like Chlamydia".
So, know I would like to ask an expert on the subject, how good protection does a condom provide?
Lets assume also that the partner I have sex with do have one STD and list the effectiveness by desease:

From what I understand, when you see a figure like "Condoms gives 70% protection against ...." this usually means 30 % risk of accuiring a STD over a year, is that correct? And that also means that the persons can have multiple sexpartners and maybee had sex 100 times?
I'm curious because if I´m told that condom give a 70 % protection against syphilis for example I don´t find that figure so reassuring even if syphilis is not that common. And there are other std´s as well....
So, I would be very glad (and maybee some other people too) if you can spread some light over how to interptret different statements in this subject. Can you also spread some light over what is meant when some say that "the infected part is not covered by the condom". Does this mean the inside of the thigh, the scrotum, the feet.... What parts of the body is susceptible for the different STD´s?

Thank you for a very good site!

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239123 tn?1267651214
Welcome to the forum.  You're asking an awful lot for a forum like this -- a whole book could be written.

You seem to correctly understand the main points about condom efficacy:  the differences between "biological" efficacy and "use efficacy"; and that when there is low risk for a single condom protected exposure, low risks can gradually become high with multiple exposures.  Biological effiacy is how well a properly used condom works for a particular exposure event; it is 100% for practical purposes against infections transmitted primarily through secretions, such as HIV, gonorrhea, or chlamydia; and somewhat lower for those transmitted skin-to-skin, like herpes, syphilis, and HPV.  Use efficacy refers to the success rate over time and with average people using condoms in average ways -- i.e. it accounts for screw-ups in use (e.g., putting the condom on only for ejaculation, but unprotected sex before then), breakage, forgetfulness, etc.  Success of condoms for pregnancy prevention illustrates the difference:  for any single exposure, condoms are probably 95% effective in preventing pregnancy; but couples who rely exclusively on condoms for contraception have, on average, a 60-70% reduction in pregnancy rates (not sure these percentages are accurate, but they're in the ballpark).

For most STDs, there are no actual data on biological efficacy.  It's just assumed based on common sense, and knowing that no infections are acquired through intact latex or polyurethane.  Most available data therefore are on use efficacy, but those data often are highly unreliable.  I cannot vouch for your figure of 70% protection against syphilis, but I imagine it comes from interviewing people with syphilis and calculating efficacy based on what they say about condom use in the past, and past recall of such things often is bad; people tend to over-estimate past use, especially if they know the "right" answer.  ("Of course I used a condom in the bath house.  Only an idiot wouldn't."  And that gets recorded as syphilils being acquired despite condom use.)  The only way to determine real use efficacy is to have people record sexual events and condom use (or not) in real time diaries and then analyze those data in connection with ongoing STD testing.  That's been done only for one STD, HPV -- and it shows about 70% reduction in new HPV infections over a year among women who report virtually 100% condom use; dropping to 50% condom use and there is no protection at all against HPV.

The bottom line is that all published information about condom efficacy, and the protection rates stated by health education sources, are very imprecise.  There is no doubt condoms reduce rates of new STD infections, especially for any particular sexual encounter if the condom is properly used and doesn't break.  And over time, consistent condom users have lower rates of all STDs than non-users or inconsistent users.  Beyond that, don't look for any precision.  How does this translate into real world advice?  Here's one example:  for a single condom-protected sexual exposure, it usually makes no sense to get tested for HIV or other STDs.  But even consistent condom users should have an HIV test and perhaps other STD testing from time to time, like once a year.

Almost all STD transmissions that occur due to skin contact above the condom involve the uncovered part of the penis or a female partner's labia.  The skin-skin STDs don't cause infection by simple contact with skin; syphilis, HSV, and HPV probably have to be "massaged" into the skin, so infection occurs only where there is friction during sex.  Getting secretions on the thighs, lower abdomen, etc carries little if any transmission risk.

It's a complex topic and I'm not going to get into a prolonged discussion about it.  But I hope this much helps a bit.

Regards--  HHH, MD
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239123 tn?1267651214
H. Hunter Handsfield, M.D.Blank
University of Washington
Seattle, WA
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