From Vaping Post:

Chelsea Boyd, a harm reduction research fellow at the more moderate, center-right R Street Institute, in Washington, D.C., agrees.

“I’m supportive of a national action to raise the minimum age of purchase to 21 for all tobacco products,” Boyd said pragmatically. “Unfortunately, by the sounds of it, only vaping products will be subject to this change, which I find problematic.”

“Combustible cigarettes are far more harmful than vapor products, yet 18 to 20-year-olds in states that have not yet adopted 21 to purchase laws would still have access to combustible products,” Boyd said.