This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. There are many studies in the marketing and diffusion literature of the conditions in whichsocial contagion affects adoption processes. Yet most of these studies assume that social interactions do not change over time, even though actors in social networks exhibit differentlikelihoods of being influenced across the diffusion period. Rooted in physics and epidemiology theories, this study proposes a Susceptible Infectious Susceptible (SIS) model toassess the role of social contagion in adoption processes, which takes changes in social dynamics over time into account. To study the adoption over a span of ten years, theauthors used detailed data sets from a community of consumers and determined the importance of social contagion, as well as how the interplay of social and non-social influencesfrom outside the community drives adoption processes. Although social contagion matters for diffusion, it is less relevant in shaping adoption when the study also includes socialdynamics among members of the community. This finding is relevant for managers and entrepreneurs who trust in word-of-mouth marketing campaigns whose effect may be overestimatedif marketers fail to acknowledge variations in social interactions.