, sorry for the delay!
What makes you think your flashdrive is infected in the first place?
About Panda, have a look here: http://hype-free.blogspot.com/2009/03/how-does-panda-usb-vaccination-work.html
And from within that link:
The “vaccination” of the USB drives: this is done by creating a folder named “autorun.inf” on the drive. Since folders and files are the same on most file systems, you can’t create a file and a directory with the same name. There is also some additional magic involved: the tool creates a file named lpt1 in the folder named autorun.inf (so you have the structure U:\autorun.inf\lpt1) in which it writes “caacaacaacaacaa” (don’t ask my why, I have no idea – it seems to be gene sequence).
This makes the folder undeletable by conventional tools.
Flash_Disinfector does pretty much the same thing if you're running WindowsXP:
Flash_Disinfector will create a hidden "dummy" autorun folder/file with special permissions in each partition and every external drive that was connected when the tool was run. This folder helps to keep the malicious autorun.ini file from being installed on the root drive and running other malicious files which will infect the computer.
Your safest bet would be to vaccinate your PC first
, then insert the USB device and vaccinate that as well
. Then scan them for malware
with a program like Malwarebytes Anti-Malware
, in that order
Does this answer your questions?