We determine the free energy of a vortex fine within the Ginzburg-Land
au formalism. Besides the usual translational modes we also take accou
nt of self-fluctuations of the order parameter in the calculation of t
he vortex free energy. The latter are due to the internal structure of
a vortex line and lead to an observable downward renormalization of t
he lower critical-field line H(c1) (T) in strongly layered superconduc
tors. In thin films the self-fluctuations of the vortex lead to a redu
ction in the power-law exponent of the current-voltage characteristic.
We argue that in a three-dimensional system the spontaneous creation
of vortex lines cannot occur.