  We evaluate the one-graviton loop contribution to the vacuum polarization on
de Sitter background in a 1-parameter family of exact, de Sitter invariant
gauges. Our result is computed using dimensional regularization and fully
renormalized with BPHZ counterterms, which must include a noninvariant owing to
the time-ordered interactions. Because the graviton propagator engenders a
physical breaking of de Sitter invariance two structure functions are needed to
express the result. In addition to its relevance for the gauge issue this is
the first time a covariant gauge graviton propagator has been used to compute a
noncoincident loop. A number of identities are derived which should facilitate
further graviton loop computations.
