PEP involves the use of HIV medication by individuals who have been very recently exposed to HIV to reduce the risk of infection. PEP is not a single tablet but a course of treatment which needs to be taken for 28 days. It is more effective the sooner it is started after exposure to the risk of HIV infection. Ideally this should be within the first 24 hours, though PEP may be offered up to 72 hours after exposure.
The principle behind PEP is that the very early use of HIV drugs may stop HIV from establishing itself in the body. It is available on prescription through sexual health clinics or hospital emergency departments, though not through GPs, and it is given at the discretion of the health professional.
PrEP involves the use of HIV medication by someone who is HIV-negative but known to be at risk of acquiring HIV. In recent years, several high-profile studies have demonstrated the effectiveness of PrEP in protecting people at high risk of HIV. Most commonly, it is one pill that is taken daily on a consistent basis. PrEP is available on the NHS and can be accessed through sexual health clinics.