Objective: E-cigarettes have achieved a high prevalence rapidly. While social media is among the most influential platforms for health communication, its impact on attitudes and behaviors of e-cigarettes and its changes over time remain underexplored. This study aims to address the gap.

Methods: Four years of data (2017–2020) were derived from the U.S. Health Information National Trends Survey (HINTS) (aged 18–64 years, n = 9,914). Initially, key variables were compared across years. Furthermore, guided by the health belief model, we employed a moderated mediation model to examine the influence of social media health communication on the public’s perceptions and behaviors related to e-cigarettes, distinguishing between smokers and non-smokers throughout the four-year period.

Results: The evidence shows a process of dynamic interaction between communication, perception, and behavior. (1) We observed an increasing trend of social media health communication (SMH) and perceived relative harm of e- cigarettes (PHE). (2) Higher SMH was associated with more e-cigarette use directly in 2019. (3) Higher SMH was associated with less e-cigarette use indirectly through PHE in 2020. (4) Smokers consistently displayed heightened sensitivity in responding to harm perception compared to non-smokers.

Conclusions: The findings support two mechanisms underlying the association between SMH and e-cigarette use: direct and indirect. The changes in the pathways during the timespan may have been influenced by increased e- cigarette information on social media and public health events like COVID-19. Stricter regulations for unverified e-cigarette advertisements and anti-e-cigarette education on social media are called for to curtail e-cigarette use.