Failure of the RA 27/3 strain of rubella virus to induce intrinsic interference -- Kleiman and Carver 36 (2): 335 -- Journal of General Virology

Unlike other strains tested, the RA 27/3 vaccine strain of rubella virus, attenuated in human fibroblasts, failed to inhibit superinfection with Newcastle disease virus (i.e. induce intrinsic interference). Since proteins of the input virion are known to lead to intrinsic interference, these may differ in the RA 27/3 strain from those in other rubella strains.