[dentist90]

Yea, the coalesence of those vesicles is sure following the progression of a herpes lesion. If it's still solitary that's great. I'm not well versed on herpes simplex of the skin, but I see these regularly on the lips, gums and palate.
And yes, shingles typically follows the dermatome distribution of the nerve affected (infected). The virus lays dormant in the nerve ganglia until the opportunity arises to break out again, often when one is ill or run down. I'm not sure what this means for the possiblity of future recurrences.

How would one get a primary infection on the back anyway, assuming this is herpes?