varicella and mumps

[Tina]

Hi everybody!

Just a simple question, may be the answer is evident for everybody, but I'm
intringated about it.
We know that when children has varicella or mumps they got better rapidly
and without big consequences. So, why this is not the same situation when an
adult person got these diseases? The immune system of children is not
supposed to be less developped than the adult one?

Thank you in advance for answers!
Tina