It is not possible to predict the COVID-19 epidemic over long time periods. This is due both to uncertainties in the epidemiological characteristic of the circulating virus variants, and because the disease transmission depends on intervention levels and people's behaviour, which is extremely hard to predict.
Therefore, we present scenarios of how the epidemic might play out given specific assumptions aboutpolicy implementation,people'sbehaviour,andotherfactorsgoverningtheepidemic,suchas the effectiveness of vaccines and the duration of natural and vaccine-derived immunity. We assume that the contact-measures implemented in each scenario do not change during the simulations. Similarly, we assume there are no changes in human behaviours affecting the contact rate. While it is possible to include in the model an effect of change of behaviour as a result of high levels of infection, this would require many assumptions on the size and thresholds of these effects for which we do not have any data. For this reason, we choose not to include such effects in the model. Because of these factors, the scenarios shown are not predictions on how the epidemic is likely to develop in the future but are the modelled outcomes of a specific set of assumptions .