Yuo will not lose Queens, that is nonesense.
It is almost impossible to OD Bees on OA
However you can OD yourself if you get too much OA vapor in your lungs and Kidney damage can occur
Coming in a bit late on this ...
Agree - there's no evidence at all of losing queens with VOA (unlike MAQS) - even with multiple doses.
I had one colony with DWV 'on it's knees' last year in mid-season, and zapped them with 4 doses of VOA, 4 days apart, just to be sure (normal recommended multi-dose is 3 doses of VOA 5 days apart - but I wasn't taking any chances). Colony survived and has just over-wintered ok.
A guy from Portugal with the same problem contacted me, and after doing the same he wrote and confirmed that the multi-dose protocol was successful for him also.
Some people are just set against using Oxalic Acid - don't know why - maybe it's because it's mode of operation is still unclear ? Myself, I don't care how it works ... I just know it does.