After the pandemic: perspectives on the future trajectory of COVID-19.

There is a realistic expectation that the global effort in vaccination will bring the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic under control. Nonetheless, uncertainties remain about the type of long-term association the virus will establish with the human population, particularly whether the coronavirus disease 2019 (COVID-19) will become an endemic disease. Although the trajectory is difficult to predict, the conditions, concepts, and variables that influence this transition can be anticipated. Persistence of SARS-CoV-2 as an endemic virus, perhaps with seasonal epidemic peaks, may be fueled by pockets of susceptible individuals and waning immunity after infection or vaccination, changes in the virus through antigenic drift that diminish protection, and reentries from zoonotic reservoirs. Here, we review relevant observations from previous epidemics and discuss the potential evolution of SARS-CoV-2 as it adapts during persistent transmission in the presence of a level of population immunity. Lack of effective surveillance or adequate response could enable the emergence of new epidemic or pandemic patterns from an endemic infection of SARS-CoV-2. There are key pieces of data that are urgently needed in order to make good decisions. We outline these and propose a way forward.