Ready to benefit from training: heterologous effects of early life immunization.

Trained immunity reflects the ability of the innate immune system to adapt via epigenetic changes in monocytes, enhancing responses to a range of microbes, thereby potentially reducing infection in high-risk populations. Examples of trained immunity at birth include enhanced resistance to infection in TLR-simulated newborn mice, reduced risk of late onset sepsis with histologic chorioamnionitis and beneficial heterologous effects of neonatal bacille Calmette-Guérin administration in reducing diverse infections during infancy. Future efforts will assess leveraging trained immunity in early life by administering 'stand-alone' innate immune stimuli or (self-)adjuvanted vaccines to protect against a broad range of infections.