That's one of the illnesses that the vax is only around 70% effective. My siblings and I were not vaxed for it and my little brother got it at about 9. He was sick for a week, but not really very sick at all. It was like a cold.
It ran rampant through my friend's school last winter-- she teaches 2-4 year olds. It's def on the up swing and making a come back. The kids in her class never got that sick, just spent about a week out of school. I have no experience with infants getting it.
Blessings of health to your family.
at 10:17 PM on Dec. 27, 2009