From National Review:

In fact, when I spoke with Carrie Wade (the director of harm-reduction policy at the R Street Institute, who also has an educational background in neuroscience and pharmacology), she told me that “it would surprise” her if “any” of the illnesses or deaths were due to nicotine. She said that she believed that people who admitted only to vaping nicotine might simply be “hesitant to admit” that they had been using a marijuana product as well, especially if they were teens — because, due to the difference in the chemical properties of nicotine from those of THC, she “doesn’t see a need for the problematic type of chemical to be in a nicotine product” at all.