Corey shook off the last jitters of the hangover pill. While it flushed out the worst effects of binge drinking, it also left him with an odd buzzing sensation in the back of his neck. Made him shivery, for some reason. Not a good state to be in while heading for a checkup.

Kamak had scheduled him for a consultation and vaccination with a semi back-alley doctor he and the crew used frequently. Dr. Theddis was, technically, a doctor, but he was also technically registered as a bounty hunter, allowing him to do work for fellow hunters without some of the paperwork and red tape medical procedures usually required. Nobody had bothered explaining to Cory what legal loopholes allowed that, but he didn’t really care. Doprel vouched for Theddis, and that was the only thing Corey needed to hear.

“I can’t go in with you, because of confidentiality and all that stuff, but it should be no problem,” Doprel assured him. “He usually only asks the medically necessary questions. Unless he’s feeling chatty.”

“What if he is feeling chatty?”

“Oh he just likes to talk about sports and things, and you don’t know anything about space sports,” Doprel said. “You should be fine.”

“Ah, alright, so I’m cool to tell him I’m ‘Uncontacted’ and all that?”

“He already knows,” Doprel said. “Kamak told him when he set up the appointment. Hard to explain why you need the universal vaccine otherwise. Most species get it as children.”

Doprel found the door they were looking for and gestured to it.

“All you, Corvash,” he said. “See you back in the lobby.”

While Doprel headed away, Corey headed in. He’d made it about two steps into the medical room when something stabbed him in the shoulder. He let out a yelp of surprise just in time for his attacker to slap his injured shoulder with some kind of putty.

“Fucking hell, what was that for?”

Turning to face his assailant, Corey saw a gray alien with an almost wooden complexion holding a very complicated looking syringe. The doctor tapped a single loose drop of blood off the tip of his instrument and then deposited it into a nearby machine.

“Trust me, it’s better if you do it quickly and the patient doesn’t see it coming. Tissues samples are tricky business,” Dr. Theddis said. He punched a few buttons on his mystery machine and observed whatever it was doing. “My apologies. I need to analyze your biological functions more closely to properly calibrate this procedure. Is the gel working? It’s less effective on some species.”

The glob of goo on Corey’s shoulder had dried up and stuck in place.

“What is it supposed to do?”

“Uncontacted, right. It prevents pain and seals minor wounds.”

After hesitantly plucking the dried glob off his shoulder, Corey saw that his shoulder did not hurt and was not bleeding, so he assumed it had done it’s job. He said as much to the doctor.

“Good, good, that helps too,” Theddis said. He tapped a few more buttons. “This is going to take a moment, so if you have any medical questions, now would be the time.”

“Uh...a couple, I think,” Corey said. “Oh, just something I’m curious about. All of the, what are they called, “Kenthat-somethings’?”

“Kentath retrogrades.”

“Thanks. We’re all sort of the same species, right?”

“Vaguely. Most retrograde species have DNA differentials between zero-point-two to zero-point-five percent,” Theddis said. “But, as you’ve no doubt seen, that can lead to some big differences.”

“Right, but like, internally, we’ve mostly got the same organs and stuff right? All the same functions?”

“For the most part. On that note, how many kidneys do you have?”

“Two,” Corey said. For some reason, he worried to himself that that might be the wrong answer. His momentary, and very weird, stress was alleviated when Theddis nodded approvingly.

“Okay, good. This gets very complicated if you have three or more.”

“Any other major points of failure I should know about?”

“As long as your blood’s red, there’s nothing else worth mentioning.”

“Well, it is in fact red, so I think we’re good. Could I ask you a couple other questions?”

Theddis nodded, and Corey continued.

“Cool, first question, maybe a bit of an odd one, is, uh...interbreeding? Is that possible?”

Theddis snapped his head away from the machine to look Corey dead in the eye.

“Why are you asking? Have you had sexual contact with an alien species?” Theddis asked insistently. “If you have, you need to be honest and tell me right now because there’s a non-zero chance an aggressive alien STD is already rotting your organs from the inside out.”

“Oh, god, jesus, no,” Corey said. “I’ve barely touched anyone, I swear. I was afraid you might say something like that, now I’m really glad I skipped going to a brothel last night.”

“Smart man, have some candy,” Theddis said. He drew some kind of alien confection on a stick from a drawer and thrust it into Corey’s hand in one swift motion. “And for the record, once we’re done here you should be able to visit as many brothels as you like.”

“Okay, might not do that, but at least I’ll have the option,” Corey said. “Back to my question?”

“Ah, yes, impregnation,” Theddis said. “It’s unlikely in the best case scenario. Very few species can achieve cross-species fertilization, and of those, none are likely to have viable offspring. I think there’s only three hybrids alive today in the universe, and all of them required significant medical intervention. In short, no, you shouldn’t be producing any space bastards from whatever shenanigans you intend. You should still take protective measures, though.”

“Can do.”

Corey had no desire to rehash middle school sex ed, so he changed the nature of his questions after that.

“How about blood transfusions? Say somebody gets shot out there in the field and-”

“Bad idea. Don’t do it,” Theddis said. “Even with the vaccine, conflicting antibodies will kill you faster than bleeding to death would. You should avoid transferring or ingesting fluids in general, really. Small amounts in various forms of oral contact or sexual encounters are usually safe, but better not to take the risk at all.”

“Noted. What about like, allergens? Should I carry around a space epipen or something in case there’s some exotic alien plant I’m randomly allergic to?”

“The vaccine you’re about to get should cover most reactions,” Theddis advised. “On the off chance that it doesn’t, well, just hope whatever you’re reacting to doesn’t kill you, because there’s nothing any injection can do to save you.”

“It sounds like most medical emergencies in space end in me dying,” Corey said.

“Well that’s true of medical emergencies anywhere,” Theddis said. He double checked his analytical machine as he spoke. “Could be worse. Couple centuries ago if you put both of us in a room together we’d both be dead from aerial viral exchange.”

Corey decided not to ask any more questions, as he could reasonably assume the answer to be “You’re going to die”. Theddis hummed something to himself and waited for his machine to finish it’s work, which it did with a loud ding, like a toaster.

“Ah, there we are,” Theddis said. He pulled up a readout of Corey’s biology and gave it a quick scan. “Good news for you, everything looks pretty close to the baseline biologically, your species is pretty middle of the road. Slightly higher iron content in your blood than most species. Might want to keep some supplements on hand if you’re not eating a lot of red meat.”

Corey made a note of that and allowed Theddis to continue.

“Higher predilection to heart failure than most too,” Theddis said. “And the microplastic content in your blood is...well, we can sweep that out for you, nothing to worry about. Should maybe send a memo to your planet to adopt bioplastics.”

“We’ve been told,” Corey said. “People don’t listen.”

“I see why you’re sticking around up here,” Theddis grunted. “Let me just plug this data into the lab and we’ll get your vaccine ready in no time. Trillions of nanomachines ready to emulate every possible viral threat and prepare your immune system for any situation.”

Theddis clapped his hands on his thighs and spun back towards Corey.

“Fair warning, now, I hope your schedule’s clear because this is going to be, and I am not exaggerating, the worst swap of your life,” Theddis said. “Your biology is going to be attacked in every possible way. You are going to feel like you are dying. That’s normal. But it’s one swap of suffering for a lifetime of protection.”

An increasingly nervous Corey stayed in his seat while Theddis plugged in a few commands and filled a syringe with a silver solution.

“You’ve got about a cycle and a half to get to a comfortable place before it starts to kick in,” Theddis warned. “Once you’re there, stay there, and don’t take any alcohol or other medications. Also, probably remove any sharp objects from the room in advance.”

“Are you sure this is worth it?”

“Do you want to have one shitty swap or risk dying of a horrific flesh-eating virus every time an alien coughs near you?”

Corey hesitated.

“Is there anything I can do to make the day less shitty?”

“No, but having something to bite down on helps keep you from grinding your teeth. Are you ready?”

“No.”

Theddis jabbed him anyway. It was always better when the patients didn’t see it coming.