In case I understood you correctly, you have come the closest to solving the puzzle. I will give the mod and the star to you.
To clarify what actually happens:
One of the vaccinations is a passive one, the other one is active.
An active vaccination happens like this: Mild, almost dead individuals of the disease are injected into one's body. The body generates antibodies to kill those disease-causing cells. Now, the body has become
immune. Person B has chosen the active vaccination and developed no further disease.
A passive vaccination is technically an active vaccination used on another body to gain antibodies which are then extracted and injected into the patient. They protect immediately, but the antibodies are not renewable. That's why that person will
not be
immune. Person A had no idea on this being the case and simply grabbed the passive vaccination. He/she became healthy, but not immune. Guess Person B simply was lucky.
So.. People that won a mod:
Ju-kun143Zexionsnowball112 with additional Kudosu starQueue is still open for NMs, but please check the rules.