Harmless childhood diseases?

ETA:- Edinburgh skeptics blog on Vaccines: A matter or rights?

It’s something you will oft see on anti-vaxxer websites – childhood diseases are harmless; things like measles, mumps, Pertussis, Rubella, Diptheria, Polio and Tetnus why no more harmful then a dose of the cold or a mild flu… A few days in bed and some calamine lotion and you’ll be fine…