Combining predictive models with future change scenarios can produce credible forecasts of COVID-19 futures

Abstract

The advent of vaccines against SARS-CoV-2 and the roll out of mass vaccination programs are thought to present the most effective means to control and even end the ongoing pandemic. However, uncertainties connected with the partial effectiveness of present vaccines, duration of immunity against SARS-CoV-2, and potential impact of variant dynamics, mean that it is still possible that the contagion could follow different future paths in different communities. Here, we use an extended SEIR for SARS-COV-2 transmission sequentially calibrated to data on cases and interventions implemented in the state of Florida to explore how these factors may interact to govern potential pandemic futures. Our data-driven forecasts indicate while the introduction of vaccinations could lead to the permanent, albeit drawn-out, ending of the pandemic if the immunity generated through vaccinations and natural infections acts over the long-term, additional futures could become possible if this immunity wanes over time. These futures will be marked by repeated waves of infection, the amplitude and periodicity of which will depend on the duration over which the immunity generated in a population will operate. We conclude that the possibility of these complex futures will require continual vigilance and perhaps fundamental changes in societal responses if we are to effectively control SARS-CoV-2.