No. It is always using the battery to heat the atty, so is always
vaping at what ever the battery delivers. It is using 5V from the USB to merely charge the battery. To have 5V vaping from a PT, you generally need a "straight-wire" PT, that is one that plugs into the USB but has no internal battery.
Additionally, the eGo is a regulated battery, and only delivers about 3.2V to the atty, not the full 3.7V. This is whether it is plugged in to the USB or not.