Heterologous effects of vaccination and trained immunity.

ABSTRACT

Vaccines are applied to large populations, but only recently has research into immunologic responses and mechanisms started to increase exponentially. Some live vaccines, such as the tuberculosis vaccine bacillus Calmette-Guérin, protect against other infections nonspecifically by eliciting complex immune responses which are not specific antibody related. These heterologous effects are explained by the concept of trained immunity. This editorial introduces five narrative reviews offering recent insights on innate and adaptive immune memory towards a variety of pathogens.