Fig 1. Example simulation of disease re-emergence using the nonseasonal SEIR model.
Parameters were set to mimic transmission of a measles-like disease in a population of 106 individuals, see Methods for model details and the full parameterization. a) The simulation was initialised above the herd immunity threshold, with 92% vaccine coverage. Starting in year 0, vaccine uptake of new born individuals drops linearly from 92% to 70% over 15 years. As vaccine uptake drops, Reff increases, crossing the critical threshold Reff = 1 shortly after 15 years. b) After the herd immunity threshold is crossed large outbreaks become possible, and endemicity is reestablished. c) Increases in early-warning signals (autocorrelation shown) precede the epidemic transition, enabling possible forewarning.