Ye, but that was a special case. He probably got that from space, so his body didn't have any experience with dealing with it. This is proven in real life, the Europeans brought diseases which they had immunity for to the americas, but the Natives didn't have any antibodies to deal with the European diseases which were common in Europe. So, they died. Adira would've been introcduced somewhat to the virus already from Outer, so her body would have built up an immunity. Basically how vaccines are supposed to work, by introducing to the body a weaker strain of the disease so that the body learns how to fight it off.
