But don't worry, Hajime can cure the victims with his totally human knowledge. He needs the antibodies from the Undead to cure the venom.
...antibodies... sure...
Which have to be taken while the undead is alive!
...I'm going to assume he's thinking he's dumbing that down for the humans who he doesn't want to have to explain to in a hurry that actually undead don't die they get sealed yadda yadda but it's amusing nonetheless. :P