Post Exposure Prophylaxis (or PEP) is the only thing that can stop a person becoming infected after HIV has entered their body.
Condoms are the best way of stopping HIV: they can be free (from your doctor or sexual health clinic), are easy to find, have no side effects, only need to be used during sex, and don’t require medical help.
However there's a thing called PEP which can stop a person becoming infected after HIV has entered their body:
PEP is an emergency measure to be used as a last resort, eg, if a condom breaks or you have a ‘slip up’ from your usual safer sex routine. PEP is a combination of powerful drugs and can be hard to get hold of, so it is no substitute for condoms, but it’s important to know about in case one day you or someone you’ve had sex with needs it.
PEP is not guaranteed to always work but has a high success rate. It is free of charge but can only be prescribed by doctors and if certain criteria are met. Sexual health and HIV clinics can provide it, as can Accident & Emergency departments of hospitals. Regular family doctors (GPs) don’t give PEP.