Fermionic and scalar corrections for the Abelian form factor at two loops

Two-loop corrections for the form factor in a massive Abelian theory are evaluated, which result from the insertion of massless fermion or scalar loops into the massive gauge boson propagator. The result is valid for arbitrary energies and gauge boson mass. Power-suppressed terms vanish rapidly in the high energy region where the result is well approximated by a polynomial of third order in ln(s/M2). The relative importance of subleading logarithms is emphasised. (orig.)