Trends in the use and dual use of factory-made combustible cigarettes, other tobacco products and electronic cigarettes: Results from South African Social Attitudes Surveys during 2007 to 2018.

"CONFLICTS OF INTEREST The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors declare that they have no competing interests, financial or otherwise, related to the current work. C.O. Egbe, S. Gwambe and M. Londani report that since the initial planning of the work they received support, 50% of APC, from South African Medical Research Council. C.O. Egbe reports that in the past 36 months, he received support for attending meetings or travel from South African Medical Research Council. O.A. Ayo-Yusuf reports that since the initial planning of the work he received support, 50% of APC, from University of Pretoria. Also, he reports that in the past 36 months he received a grant from Africa Capacity Building Foundation (Grant no. 326)."

"FUNDING This work was partly supported by a grant from The African Capacity Building Foundation (Grant no. 326), received by OAA. The funders did not have any influence on the writing of this article or the results presented here."