|4th try, would really appreciate a response (STATISTICS)
Aug 2, 2007
Hi Dr. Bob. At least I am re-wording the question each time to try to keep you from getting bored.
Anyways, I am trying to better understand a women's risk of HIV transmission from providing fellatio without the use of a condom. Specifically I would like to know how this risk compares to having vaginal intercourse without a condom.
The CDC per act transmission rate estimates say that unprotected receptive fellatio carries a tranmission risk of 1 in 10,000 and that unprotected receptive vaginal intercourse carries a risk of 10 in 10,000. I was surprised that the difference in risk is not greater, as I was under the impression that unprotected fellatio carried very low risk whereas unprotected intercourse was high risk.
I know that the way they arrived at these estimates involved a lot of guess-work and was not the most scientifically sound process. Do you suspect that the difference in risk is actually much greater than a factor of 10, say more like a factor of 100? (For the sake of argument, assume ejaculation in the mouth for the acts of fellatio.)
I know many women who would never have unprotected intercourse with a man they recently met whose HIV status is unknown, but who do not worry about putting on a condom for oral sex. I think they might re-think this if these estimates were close to accurate and that for every 10 times they perform fellatio without a condom it is the equivalent of 1 act of unprotected intercouse. On the other hand, if the difference in risk is much greater than these estimates imply, then maybe their different treatment of these acts is a good compromise.
Thanks for your time.
| Response from Dr. Frascino
I have not answered your previous questions, because you are confused primarily about statistical analysis, rather than HIV risk. The purpose of the CDC's estimated-transmission-risk statistics is to provide information about relative risk of acquiring HIV from various activities. These statistics do not suggest that "every 10 times someone performs fellatio without a condom is equivalent to one act of unprotected intercourse!" Rather, they indicate that unprotected receptive penile-vaginal sex is 10 times more risky than oral sex. This is a very significant difference! What's more important to realize is that these are only "estimates" and that there are many individual factors that come into play in any one particular exposure that can significantly influence HIV transmissibility. These include both viral factors, such as viral strain and viral load, as well as host factors, such as immune integrity and the presence of concurrent infections. What people should take away from the CDC's estimated-transmission-risk statistics is that oral sex is much less risky than vaginal sex, which in turn is much less risky than anal sex. Also, the receptive partner is always at greater risk than the insertive partner, no matter what type of penetrative sex you might be enjoying, OK?
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