Modern MANPADS as I understand it also utilize an ultraviolet sensor to overcome thermal decoying. The idea is that the aircraft body will show up against the sky due to reflecting UV light, and more significantly the engine plume of a jet aircraft, especially one under afterburn, produces a significant amount of UV light.
Decoy flares, on the other hand, do not produce any UV.
So, when working together, the IR sensor may be momentarily confused by decoy flares, but the UV sensor will remain fixed on the aircraft and get the IR sensor back on track.
Blinding lasers remain effective, of course.