  One-loop corrections to $\omega$ photoproduction near threshold have been
investigated by using the approximation that all relevant transition amplitudes
are calculated from the tree diagrams of effective Lagrangians. With the
parameters constrained by the data of $\gamma N \to \pi N$, $\gamma N \to \rho
N$, and $\pi N \to \omega N$ reactions, it is found that the one-loop effects
due to the intermediate $\pi N$ and $\rho N$ states can significantly change
the differential cross sections and spin observables. The results from this
exploratory investigation suggest strongly that the coupled-channel effects
should be taken into account in extracting reliable resonance parameters from
the data of vector meson photoproduction in the resonance region.
