Failure of pre-exposure prophylaxis with daily tenofovir/emtricitabine and the scenario of delayed HIV seroconversion.

Failure of pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine may occur despite perfect adherence, although this is uncommon. Failure results in breakthrough HIV infection. Delayed seroconversion associated with antiretroviral use may complicate the picture, causing uncertainties in interpreting adherence patterns for establishing the true cause of PrEP failure.