This 2020 review subject was the normal progression of our immune systems:

“Age-related alterations in the immune system result in high susceptibility to infections, increased risk of hospitalization and mortality. Defects in adaptive immunity underlie the markedly low vaccine efficiency in the elderly. Despite reduced cellular functions, a systemic increase in inflammatory markers, so-called inflammaging, is observed in aged individuals.

Trained immunity is a newly emerging concept that showed that innate immune cells possess non-specific immunological memory established through epigenetic and metabolic reprogramming upon encountering certain pathogenic stimuli.

Novel approaches targeting innate immunity to improve host responses are crucial to evade the consequences of the aged immune system. It is an emerging concept that innate immune cells can manifest memory-like properties that are not antigen-specific and exhibit enhanced responsiveness upon later challenges with heterologous stimuli. Whether trained immune responses change as people age is yet to be explored.”

https://academic.oup.com/intimm/advance-article/doi/10.1093/intimm/dxaa052/5885077 “Overcoming immune dysfunction in the elderly: trained immunity as a novel approach”

Previous papers by this review’s corresponding coauthor were curated in:

• Trained immunity responses to bacterial infections;
• Immune memory vs. immune adaptation; and
• A dietary supplement that trains the innate immune system.

There’s no reason to rely entirely on the review’s elaborate vaccination schemes to develop trained immunity. Take responsibility for your one precious life and Train your immune system every day!