Try to think of these years as preperation for the rest of thier lives. Your child is going thru what all kids do, teaching the body whats good and whats bad:
"A child’s immune system is not fully developed before the age of 14, making kids under this age particularly susceptible to infection and sickness. What little immunity they do start life with is passed on from the mother via the placenta (before birth) and then in breast milk. This is known as passive immunity and is fairly short-lived.
A more active and longer-lasting immunity is acquired following exposure to infection, which then stimulates the immune system to respond. This exposure can be to an infection like the common cold, caught from someone else, or through immunization."
http://www.whatreallyworks.co.uk/sta...article_ID=559
We all worry that OUR kid is sicker than most....but most of us are wrong...heh.