PEP:

Post-exposure prophylaxis (PEP) is a treatment that decreases the risk of infection after exposure to HIV in persons who test negative for HIV at that time. PEP should start as soon as possible after exposure to HIV. It may no longer be effective if started more than 72 hours after exposure.   

PEP must be taken daily for 4 weeks. A new test for HIV is performed at the end of this period.  

It is prescribed by physicians.