It may not be as bad as smoke, but that's not the same as "doesn't harm"—the jury's still out on that.

Also, not all vaporizers are created equal. Are you using the type that heats plant material to a temperature that the cannabinoids are released, or the e-cig type that uses some type of solvent?

As I understand it, some (perhaps not all—don't know) of the e-cig type use the same kinds of solvents (e.g. glycerin, propylene glycol, and others) used for nicotine delivery.

Carbonyl Compounds in Electronic Cigarette Vapors-Effects of Nicotine Solvent and Battery Output Voltage.

Health risks of e-cigarettes emerge

e-cig solvents medical marijuana

Bottom line: make sure you know what you're inhaling.

Doc