Pre-exposure prophylactic treatment (PrEP) for HIV is commonly said to reduce infection rates by more than 75%.
Similar treatments for already-infected patient treatments do not cure HIV, but reduce viral load to undetectable levels. If treatment of these patients is stopped, viral load will eventually rise.
Do we know that PrEP actually prevents infection, rather than masking it? Are there no cases of someone engaging in no risk behaviors, then going on PrEP and engaging in risk behaviors, then coming off it, not engaging in any further risk behaviors, and nevertheless testing positive for HIV?