[en] We have used the resistive pressure gradient driven instability model to study the effect of plasma on a vacuum magnetic field island. We have studied under what conditions the island is amplified or reduced. Starting with a set of reference parameters, we have varied these parameters by increasing either the density or the electron temperature. These scans lead to very different results. When beta increase because of the increase in density so does the island width. However, in the case that beta is increase by increasing the electron temperature, we observe a decrease in the island width. The main mechanism for island reduction seems to be the generation of strong sheared flow associated with the magnetic island. These results seem to reflect some observations in the LHD device. (author)