How soon after occupational exposure should PEP be started to be effective, and what is the recommended duration of treatment?

The optimal time frame for initiating post-exposure prophylaxis (PEP) following occupational exposure is as soon as possible, ideally within 1 to 2 hours, and no later than 72 hours after exposure to ensure its effectiveness. Initiation beyond 72 hours is generally not recommended due to significantly reduced efficacy.

The recommended duration of PEP treatment is 28 days (4 weeks). This duration balances maximizing viral suppression and minimizing adverse effects.

This approach aligns with UK clinical guidelines emphasizing prompt initiation of PEP ideally within hours of exposure and continuing treatment for 28 days to reduce the risk of seroconversion ¹. Similarly, the updated US Public Health Service guidelines recommend starting PEP as soon as possible, preferably within 1 to 2 hours, and no later than 72 hours post-exposure, with a 28-day treatment course (Kuhar et al., 2013). Belgian guidelines for non-occupational PEP also support this timing and duration (Libois et al., 2018).

In summary, to ensure optimal effectiveness of occupational PEP:

• Start PEP immediately, ideally within 1–2 hours, and no later than 72 hours post-exposure.
• Continue the prescribed antiretroviral regimen for 28 days.

This integrated recommendation reflects consensus across UK guidelines and international literature, emphasizing the critical importance of rapid initiation and adherence to a full 28-day course to maximize prophylactic benefit and reduce HIV transmission risk.