Comparison of e-cigarette use prevalence and frequency by smoking status among youth in the United States, 2014-19.

"Declaration of interests None."

"This analysis was partially conducted while J.T. was a Tobacco Regulatory Science Fellow at the US Food and Drug Administration Center for Tobacco Products. She is immensely grateful to Drs Gabriella M. Anic and Karen Cullen for their expert guidance, feedback and support of this project from 2018–19. J.T. did not receive grants from any funding agency in the public, commercial, or not‐for‐profit sectors for this work. A.B. is funded by the National Cancer Institute (NCI) and Food and Drug Administration (FDA) grant U54CA229974. The opinions expressed in this article are the authors’ own and do not reflect the views of the National Institutes of Health, the Department of Health and Human Services, or the United States government."