Most likely it is, although there is always the possibility that the ridges and grooves on the axle or the wiper have been stripped. (Did you have the wipers on when you parked one night so that they had to break out of some ice in the morning?)
Even with the pieces stripped, tightening the screw should probably hold it together long enough to buy replacements.
Less likely, though possible, is that the arm from the wiper motor extending left (if you have a single motor) has broken free inside the hood or that the motor on the left (if you have a one-motor-per-wiper arrangement) has either burned out or come unplugged.