Evaluating the impact of plain packaging among Canadian smokers: findings from the 2018 and 2020 ITC Smoking and Vaping Surveys.

Plain packaging in Canada substantially reduced pack appeal and increased support for the policy among adult smokers; however, there was no increase in the effectiveness of Canada's 8-year-old HWLs. The impact of plain packaging on health warning effectiveness may depend on the design of the warnings and length of time since implementation.