PEP is a medication regimen. Some folks compare it to emergency contraception aka "the morning after pill" which is actually two pills taken twelve hours apart or together or a whole bunch of birth control pills or IUD insertion and all the pill options are effective up to 120 hours (5 days) after unprotected vaginal intercourse and IUD insertion is good up to seven days later so it's hardly a "morning after pill" but that's another discourse. However, the discourse is similar.
PEP is hardly a morning after solution. It is a full anti-retroviral medication regimen. It must be started within 72 hours (3 days) after exposure and continued for 28 days. And, depending on the medication, can come with quite a load of side effects. Not exactly popping a pill and forgetting about that little indiscretion.
Here's an article
and here's the CDC release
it's about time.