For we know that the whole creation groaneth and travaileth in pain together until now.
Romans 8:22
".....scientists established that COVID-19 leaves behind long detectable changes in the blood of convalescents, very similar to a fingerprint.
For example, the number of granulocytes, which are otherwise 
responsible in the immune system for fighting bacterial pathogens, is significantly lower than normal in the COVID-19 group. Pickl explains: “However, both the CD4 and CD8 T cell compartment developed memory cells and CD8 T cells remained strongly activated. This indicates that the immune system is still intensively engaged with the disease several weeks after initial infection. At the same time, the regulatory cells are greatly diminished – and that is likely a dangerous mix, which could lead to autoimmunity.” Furthermore, increased levels of antibody-producing immune cells were detected in the blood of convalescents – the higher the fever of the affected patient during the mild course of the disease, the higher were the antibody levels against the virus.
Above all, the study shows that the human immune system “doubles up” when defending against COVID-19 with the combined action of immune cells and antibodies – like the defense in a modern soccer team – and that the cells are also able to memorize certain “moves” on the part of the virus (Note: “memory”) and respond to them. Now it is a matter of implementing these findings and using them for the development of highly-effective COVID-19 vaccines.”
SciTechDaily