mild to major . In the pre vaccine era most chicken pox cases were minor, yet it was known to produce 50-100 deaths/yr in the us. With 10 thousand hospitalizations, a 50 fold increase in invasive strep risk, reyes syndrome, encephalitis, ataxia & other issues. After vaccine use started, the numbers have declined but any child with wild chickenpox disease may experience any of those complications.
Varied. Although chicken pox is generally considered more of a nuisance illness by many complications can be quite severe. Complications of chicken pox include bacterial infection of the skin lesions, pneumonia, encephalitis (brain involvement), glomerulonephritis (kidney involvement), arthritis, hepatitis (liver involvement), and reye syndrome.