Diabetes has been documented as a symptom of cytomegalovirus (mono), mumps, rubella, rotavirus, and enteroviruses (polio and hand-foot-mouth). Fatigue is a symptom of lyme disease and mono.
I don't want my kids to get any of those either, and they were vaccinated for mumps, rubella, rotavirus, and polio by age 1. If I have the choice of being cautious for 3 months until a vaccine is available for COVID, I'll take it.
https://en.wikipedia.org/wiki/Cytomegalovirus
Most cases of mono are caused by EBV, but CMV primarily presents as mono, and sometimes pneumonia.
EBV/mono is another common childhood illness with lots of nasty potential chronic complications, including lymphoma, other cancers, CFS, and autoimmune diseases like lupus, MS, and rheumatoid arthritis.