M.R.
Straight from the CDC's vaccine information sheet:
1st dose is between 12-15 months of age
2nd dose is between 4-6 years of age
"Chicken pox is a common childhood disease. It is usually mild but it can be serious, especially in young infants and adults...it can lead to severe skin infection, scars, pneumonia, brain damage, or death."
"Before the vaccine, about 11,000 people were hospitalized for chickenpox each year in the United States."
"Before the vaccine, about 100 people died each year as a result of chickenpox in the United States."
"Most people who get chickenpox vaccine will not get chickenpox. But if someone who has been vaccinated does get chickenpox, it is usually very mild. They will have fewer blisters, are less likely to have a fever, and will recover faster."
"A person who has had chickenpox can get a painful rash called shingles years later."
So, as you can see, the numbers aren't high at all but they're not zero.