A follow on to I Got Natural Eemunity

You know when I was a kid in a large family
We never had much money
So we had a bath only once a week
Simply because heating water cost money
Something we didn't have
A simple way of life eating simple food
Anyway days at school were spent alongside rich kids
In their spotlessly clean uniforms
With their sniffles and coughs and runny noses
Spluttering over their hygienically prepared lunch boxes
But
Us poor kids with a cheese sandwich in a paper bag
Rarely got a cough or cold