Adaptive immunity involving B cells and T cells can be compromised by reduced cell function, hindering the body's response to coronaviruses.

“we get our long-term immunity through our adaptive immune system so b cells producing antibodies gives us several months of immunity t cells can have memory lasting decades so if you have a reduction in t and b cell function your long term adaptive memory of a coronavirus let's say a common cold you got 10 years ago which may have now looked at the structure of this new coronavirus and you may have had some cross sensitivity and remembrance but if you have a reduction in that memory now your previous adaptive immunity isn't helping you with sars code too”