Since neither death or disease are part of the curses found in Genesis 3 the issue of immunity would be moot. As referance here are the pertenent sections of Genesis 3.
16 To the woman he said,
"I will greatly increase your pains in childbearing;
with pain you will give birth to children.
Your desire will be for your husband,
and he will rule over you."
17 To Adam he said, "Because you listened to your wife and ate from the tree about which I commanded you, 'You must not eat of it,'
"Cursed is the ground because of you;
through painful toil you will eat of it
all the days of your life.
18 It will produce thorns and thistles for you,
and you will eat the plants of the field.
19 By the sweat of your brow
you will eat your food
until you return to the ground,
since from it you were taken;
for dust you are
and to dust you will return."
There is nothing in those that has anything to do with disease or other than the acknowledgement that after you die your body will return to the earth. Neither appear as anything new or related in anyway to the curses of Genesis 3.
Aslan is not a
Tame Lion