Thank you in advance for providing me helpful information! Fifty-two y.o. single gay man who is neg and have been on Prep for over a year. I take it every day every week. I very rarely engage in anal sex and when I do, I am always a top and now bareback. (And btw the first I did it BB, I got gyn. and chlam.!). So now as far as unknown partners, once every 2-3 months I go to a sex club and suck 2-3 guys to completion and swallow. I have read that PREP studies were based on killing the virus in anal tissues but what about mouth, throat, esophagus, etc. Am I being silly to still be anxious about contracting HIV that way? My whole sexually active life I feared hiv and Hope PREP might ease my fears to enjoy sex more when not in a monog relationship.
Thank you for writing in. I can understand that it ca be difficult to relax, suck guys off, and enjoy sexual expression without fear of HIV or punishment of some sort. But based on what you are describing, you are at no risk of acquiring HIV from oral sex. Here's why:
(1) PrEP has been found to be 99%+ efficacious for any person who uses it four or more times a week. With over 12,000 "high-risk" individuals having volunteered in efficacy trials and demonstration projects, the research has shown that PrEP works extremely well for anal and vaginal sex when used consistently. As a matter of fact, no one who participated in these first set of trials acquired HIV when they took Truvada as directed (http://www.natap.org/2016/ICAAC/ICAAC_02.htm; https://www.robertmgrant.org/project/has-prep-ever-failed/). If your theory was correct, that PrEP only protected for anal or vaginal sex but not oral, then there could have been more HIV transmissions in the trials. But again, there were not.
(2) Even without PrEP, your risk of acquiring HIV from oral sex are nearly zero. The CDC considers oral sex on par with kissing and touching as far as possibility of HIV acquisition (https://wwwn.cdc.gov/hivrisk/estimator.html).
The PrEP trials you mentioned weren't so much about killing the virus as it was about not allowing the virus to duplicate and replicate if it enters the body. PrEP offers significant protection to IV drug users as well, which demonstrates how well it PrEP protects the whole body, not just the ass and genitals. (http://www.aidsmap.com/PrEP-works-for-injecting-drug-users-too/page/2678439/).
I hope this information enables you to relax and experience the sexual encounters you enjoy with pleasure and confidence. You are doing everything medically possible to play with others and reduce risk. Have fun!