There is still a chance of transmitting HIV while taking blocking medications (e.g. tenofovir, emtricitabine, raltegravir). If there is a risk of exposure to HIV and the blocker is taken within 72 hours, the success rate of the blocker is 95%, but there is still a chance that the blocker will be unsuccessful and therefore HIV transmission is still possible. All blocking medications should be taken under the supervision of a medical professional. In addition, if the amount of HIV exposed at the time of infection is extremely high, for example, if a patient is infected by transfusion of HIV-contaminated blood, the amount of virus in the body is high at the beginning of infection and the time required for the virus to multiply is much shorter, even if the blocking medication is taken, the patient is still contagious. Until successful blockade is established, effective preventive measures should be actively pursued to avoid spreading the virus to others as much as possible.