15 months. I've seen it in a 15 mo.in the pre vaccine era. Some suggest an infection, recognized or not, during pregnancy can pass the germ to baby, who may then develop shingles at any time. It is rare, & only saw one in toddlers in almost 40 yrs of practice but it does happen. When suspected, it should be confirmed with an office visit.
No. The youngest shingles patient i've ever treated was 3 -- and it's very rare for someone that young to get it. Normally, chicken pox is the childhood version of the disease, and shingles is the adult version. Babies rarely get either version, because for the first year of life they are protected by their mother's antibodies. That's why kids aren't immunized against chicken pox until age 1.