Post-Exposure Prophylaxis (PEP): Quick Facts and Practical Steps

Post‑exposure prophylaxis, or PEP, is a short‑term treatment you take right after a possible infection. It can stop HIV, hepatitis B, rabies and a few other germs from taking hold. The idea is simple: start the right drugs fast, keep the dose steady for the recommended days, and you lower the chance of getting sick.

When to Start PEP

The clock matters. For HIV, you have about 72 hours after exposure to begin a three‑drug regimen. The sooner you start, the better the protection. If you’re unsure about the risk, talk to a doctor or go to an urgent‑care clinic right away. Hepatitis B has a slightly longer window, but getting a dose of hepatitis‑B immune globulin (HBIG) and the vaccine within two weeks works best. Rabies PEP should start as soon as possible, ideally within a day, because the virus spreads quickly to the nervous system.

Common PEP Regimens and What to Expect

For HIV, most providers prescribe tenofovir + emtricitabine plus an integrase inhibitor like raltegravir or dolutegravir. You take the pills twice a day for 28 days. Side effects can include nausea, headache, or mild fatigue, but they usually fade after the first week. Hepatitis B PEP uses a single shot of HBIG and the first dose of the hepatitis‑B vaccine, followed by two more vaccine doses at one and six months. The injection can be sore, but serious reactions are rare.

Rabies PEP combines a dose of rabies immune globulin with a series of four rabies vaccine shots on days 0, 3, 7 and 14 (or 0, 3, 7 and 28 depending on the brand). The shots may cause soreness at the injection site and a brief fever. You’ll need a follow‑up blood test to confirm the vaccine worked.

Getting the meds is easy once you have a prescription. Many pharmacies offer PEP pills or injectables, and some telehealth services can send them straight to your door. Keep a reminder to take every dose on time; missing pills reduces effectiveness. If you notice a rash, severe stomach pain, or trouble breathing, call your doctor right away.

After finishing the course, most providers will ask for a follow‑up blood test to check for infection. This usually happens four to six weeks after you start PEP. If the test is clean, you’ve likely avoided the disease. If not, your doctor will discuss next steps.

Bottom line: act fast, follow the schedule, and stay in touch with your health provider. PEP isn’t a guarantee, but when used correctly it cuts the risk dramatically.