  The properties of compact stars made of massive bosons with a repulsive
selfinteraction mediated by vector mesons are studied within the mean-field
approximation and general relativity. We demonstrate that there exists a
scaling property for the mass-radius curve for arbitrary boson masses and
interaction strengths which results in an universal mass-radius relation. The
radius remains nearly constant for a wide range of compact star masses. The
maximum stable mass and radius of boson stars are determined by the interaction
strength and scale with the Landau mass and radius. Both, the maximum mass and
the corresponding radius increase linearly with the interaction strength so
that they can be radically different compared to the other families of boson
stars where interactions are ignored.
