We now have confirmation of a case where HIV was transmitted to a man who was faithfully using PrEP. Apparently, the HIV he encountered was resistant to the meds in Truvada.
PrEP is said to be up to 99% effective, but it is not 100% effective, as this case shows. On the bright side, it's (so far) just one case out of 40,000 or so people on PrEP.
One thing I think is inarguable about PrEP—and yet something that was argued by PrEP boosters early on—is that gay men think PrEP is basically 100%, and they are not using it in conjunction with condoms. A glance at any hookup site or app reveals that guys are aggressively seeking condomless anal sex and promoting themselves as on PrEP.
The nightmare outcome would be that PrEP protects people from HIV in the short run before leading them to expose themselves to drug-resistant strains of HIV and other STIs. Hopefully, this case will be an anomaly rather than a canary in the coal mine.
I don't think this case should mean we throw out PrEP, but it should be a warning to take casual anal sex more seriously; we aren't out of the woods yet.