He's said to have been bitten by an infected and amply survived. We see the bite mark, mostly healed, on his shoulder. So what's going on?
Possibly he has some kind of natural immunity to the plague bug. This would be consistent with what we know of deadly plagues in our own off-screen reality. Even the deadliest plague has some survivors, however few. If there were a scientific community of researchers who could study the pharmacist, his immune system could provide a key to fashioning some kind of mass immunity injection. This, of course, could and would change everything.
Another possibility, given that he is a pharmacist, is that he concocted some kind of drug treatment for the plague, and it worked on him. If that was the case, then all the possibilities described above for natural immunity would apply - scientific researchers could mass-produce the drug, which in turn would change everything.
Of course, in both cases, the pharmacist needs to get in touch with researchers - and they are in increasingly short supply in this infected world.
A third possibility, probably the most likely but the least interesting and the least fun, is that the pharmacist was bitten, but not by someone infected by the plague. Given his talk about coming back from the dead, he certainly thinks he was bitten by a genuinely infected. I hope he's right about surviving an infected bite, but you never know.
Meanwhile, we got a great hotel from hell in last night's episode - the only thing missing was the Eagles' "Hotel California," which could have been playing the background.
Looking forward to more.