Aging impairs the immune system's ability to recognize foreign pathogens, build T-cell and B-cell reserves, and maintain memory cells.

“Is it because a their immune system, the adaptive immune system is less able to recognize the foreign pathogen and build up a high enough reserve of T- cells and B cells that will respond? or is it B that they can do that but the ability for those cells to stay in a memory state and be reactivated is somehow impaired.”