Computer vaccination
By vaccinating the computer you completely disable the AutoPlay feature, so that no program on any USB/CD/DVD drive will be automatically run, regardless of whether those drives or devices have been previously vaccinated.
USB drive vaccination
By vaccinating a USB device, the vaccine blocks file Autorun.inf permanently to stop malware from spreading automatically. When a vaccine is applied to a USB drive, the file Autorun.inf is permanently blocked, preventing it from being read, deleted or modified. Once the vaccine has been satisfactorily applied, it will prevent Windows from automatically running any malware found on a USB drive. After vaccination, the USB drive will continue to work properly, but no multimedia files it might contain will run automatically.
It is important to bear in mind that USB drive vaccination is an irreversible process. Under extremely unlikely conditions, certain applications might stop working correctly. In any event, if your USB device doesn't contain the file Autorun.inf , it is completely safe to vaccinate it.