Resistance to emtricitabine plus tenofovir disoproxil fumarate (FTC/TDF) or TDF alone used as preexposure prophylaxis (PrEP) has been detected in individuals who initiated PrEP during unrecognized acute HIV infection and, rarely, in PrEP breakthrough infections.
K65R, M184V, and A62V resistance mutations developed in 1 participant in the TDF-FTC group who had had an unrecognized acute HIV infection at enrollment.