The COVID-19 pandemic has generated global perturbations in our daily lives that are unprecedented in scale. Since early 2020, changes in contact patterns and mobility have affected the regular seasonal cycles of many infectious diseases globally, including influenza. A better understanding of the effect of these perturbations can shed light on key epidemiological mechanisms that remain unclear despite decades of research. These include the strength and mechanisms that drive seasonality in transmission, the persistence of immunity from natural infection, the evolutionary bottlenecks operating during low transmission seasons, and the impact of non-pharmaceutical interventions (NPI) that could be used in future influenza pandemics.