Captain America had his Super- Soldier Serum removed for a time during the
Streets of Poison storyline of the early 1990’s. At what point did he get it
Ah, yes: Mark Gruenwald’s (almost) decade-long run on Cap seemed to throw in everything but the kitchen sink — there was Cap resigning, Cap turned into a teenager, Cap-Wolf (Don’t ask. Seriously: don’t ask), and many other variations. Through it all, he was always able to nail Steve Rogers’ essential optimism, patriotism and refusal to ever, ever give up. Older fans rolled their eyes at much of this, but those who were, say, 12 years old and started reading Cap during the Gruenwald years have a ton of fond memories of it. It was a perfect kids’ superhero comic, without ever advertising itself as one.
Anyway, the “Streets of Poison” story (um… Cap #’s 373-378?) involved an explosion in a drug warehouse that caused the street drug “ice” (Marvel’s version of crack) to interact with the super-soldier serum in Cap’s blood, and make him nuts. He ended up having to undergo some kind of dialysis to remove the serum, leaving him a normal human. Then, at the end of the arc, when he was offered a chance to have it put back, he refused: he made a speech about how, essentially, relying on the serum was like relying on artificial stimulants, or steroids, or whatever, so it sent the wrong message to kids, and he’d just be a highly-trained, regular guy instead now, thanks very much.
This lasted about six months, until issue #384, when Rogers wondered, reasonably enough, why he still seemed so fit, and able to hold his own against the bad guys. Medical tests showed that his body had rebuilt the super-soldier serum, and it was back in his blood. There was a bunch of gobbledygook about how it wasn’t actually a “serum” (which would have worn off long ago), but a “virus,” and a permanent one, so that he’d always have his abilities. Well, until Cap #425, when the virus’s ability to repair his cells started to deteriorate, and… but that’s another story.