IIRC how they make shots reactive (like a general polio shot) is they breed the viruses using cloned fetal cells from infants who were I think stillborn sometime in the 50s. Then they either kill them or weaken them, and lastly fill it with a filler chemical like saline, and you now have a polio shot ready to go.
DNA strands from fetal tissue are in vaccines so you're getting extra XX and XY chromosomes, but I'm sure that's not a factor (sarc)
IIRC how they make shots reactive (like a general polio shot) is they breed the viruses using cloned fetal cells from infants who were I think stillborn sometime in the 50s. Then they either kill them or weaken them, and lastly fill it with a filler chemical like saline, and you now have a polio shot ready to go.