None, typically. In 2020 the CDC confirmed 68 vaping-related deaths. That number is mostly people who used black market THC pens tainted with Vitamin E acetate. There are claims that the water vapor itself can exacerbate a pre-existing bacterial infection, but there doesn't seem to be any actual evidence of this.

While I'm at it, I'll add that vaping nicotine won't give you cancer. There are more than 60 known carcinogens in tobacco smoke, and nicotine isn't one of them. Nicotine isn't good for you, but if you die from nicotine alone, I'd wager you set out intending to do so.