Recently I engaged in vaginal sex with condom. however, halfway into it I noticed that my penis started to become flaccid and the condom moved up, leaving the lower part of my penis shaft exposed. Though the head and  foreskin was fully covered by the condom, and I did not see any actively bleeding cuts on the shaft, I am worried that I might be at a high risk exposure. On consulting my friend , who is an ER doctor, He told me its unlikely to catch HIV this way as the virus either needs to be introduced to the blood stream by a bleeding wound or directly absorbed by the mucous membrane. he further added that the lower part of the penis shaft consists of tougher skin and HIV is usual transmitted through the urethra or the innerside of the foreskin, both of which was covered by the condom. however, id like to have a second opinion on this matter from experts in this field. kindly tell me what my real risks are for HIV from this exposure. thank you.

I agree entirely with your doctor friend's assessment. On this forum, we have always advised that condom protection is considered complete and effective as long as the meatus (urethral opening) and head of the penis remain covered; and that exposure of the penile shaft is no more risky for STD transmission than exposure of skin anywhere else on the body. Indeed, a certain amount of such exposure probably occurs in the majority of condom-protected vaginal sex exposures, i.e. skin-to-skin contacts and exposure to genital fluids above the condom. This is why condoms are generally considered less effective against those infections transmitted by skin-skin contact (HPV, HSV, syphilis) than those transmitted primarily through genital fluids (gonorrhea, chlamydia, HIV).

That said, there are no firm data and I cannot give you an exact numerical estimate of the "real risks for HIV from this exposure", but it must be exceedingly low. You don't describe your partner for this event, but even among the most sexually active females, including sex workers, do not have HIV -- even among those at highest risk under 1% have HIV; for other women the likelihood is generally under one chance in a thousand. The average HIV transmission risk for each episode of unprotected vaginal sex with a known infected woman has been calculated by CDC as about one chance in 2,500. Even with partial condom slippage, you can assume the condom was around 99% effective in preventing transmission of HIV. Considering all those aspects, your risk of HIV probably is well under one in a million.

So I would consider this episode to be very safe, without a clear need for HIV testing, at least not from a medical/risk perspective. Some people in your situation seek testing anyway; a negative test result often is more reassuring than professional opinion, no matter how expert. (We don't take it personally!) If so, you can have a nearly conclusive AgAb (4th generation) HIV blood test 4 weeks after the event, or 6 weeks for 100% reliable results.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

Two follow-up questions or clarifications are included with each new question, so this ends this thread. I hope the discussion has been helpful.