The screening and renormalization of the Coulomb repulsion in the cond
uction band of a two-band model are considered. It is shown that when
the second band lies above the conduction band and it is empty at low
temperatures, the transfer of pairs of charge carriers between the two
bands is the relevant interband process for reducing the Coulomb repu
lsion in the conduction band. By considering a two-band situation aris
ing from the hybridization of the conduction band with shallow impurit
y states having a large intrasite repulsion, it is shown that the pair
-transfer process is effective in reducing the Coulomb repulsion even
in situations where the second band is very narrow and possesses by it
self a very large repulsion. The implications for enhanced pairing in
systems with the appropriate band structure or in those near the metal
-insulator transition caused by doping, are discussed.