I was bit at 5 years old. Was a very active and healthy kid after being bit. My Lyme + co's was dormant until 22, caused my Hypothyroid diagnosis at 23, and then eluded lab tests until 2016.
From 22 - 23, I had a very emotionally rough year, which affected my immune system and thus allowed the Lyme to creep out and gain new real estate in my body.
100% Yes it can be dormant, even for decades.
10/2006 - Diagnosed Hypothyroid + Hashimotos
10/2016 - Positive WB (Band 41) thru Quest Diagnostics
01/2017 - Igenex positve IgM for Lyme (Bands 31, 34, 39 (I), 41, 58, 83-93 I)
01/2017 - Igenex positive IgG for Babesiosis Duncani