The perplexing question of trained immunity vs adaptive memory in COVID-19.

The wide spectrum of symptoms observed in coronavirus disease 2019 appears to defy explanation. Apart from geographic limitation to people with prior exposure to other coronaviruses and air pollutants, inflammatory comorbidities and older ages are also among the main factors of susceptibility to severe illness. The unusual epidemiological data pointed out in children and African territories have revealed new insights in host-pathogen interplay with more focus on epigenetic regulation of cognitive compartments belonging to innate immunity. Should trained immunity be proven to be involved in timely immune responsiveness against severe acute respiratory syndrome coronavirus 2 and that adaptive memory could be detrimental, both treatment regimens and vaccine design will tremendously change accordingly with more focus on upper respiratory tissue innate immunity to subdue this threat underway.