Wow, no. That sounds good but that's not what would happen.
The baby would provide no resistance, as it isn't even sapient.
Although ACTUALLY a yeerk couldn't get in at all, because the baby's ear is too small; Visser 3 said cats were too small to infest, and a baby's ear would be smaller.
Very good points. It is possible that a baby's ear would be too small to get inside, but even if a Yeerk could get in then it would not encounter a strong mind. As far as scientists can tell, babies don't become completely self aware until about 2 years of age I believe. A baby's brain is also significantly smaller than that of a fully grown adult.