It's the all-new "standard" slowly spreading around the world. It should be at least as safe as SIM cards were for 25+ years before them... and conceptually (perhaps) safer. Proceed with confidence if dealing with a reputable cell service provider. If dealing with some no-name when visiting some third world country, do some quick research to verify some reviews/ratings/experiences.
Note that there is no "card." Or you might think of it as a virtual card. It's basically digital key to digital lock- nothing physically tangible involved.