And this (from the above paper) is why we still have not really got much of a clue about how to deal with COVID's effects, or how best to boost useful immune response to it:
Peripheral immune cells of COVID-19 patients were enriched in T cells, NK cells, and γδ T cells with a highly activated phenotype and elevated expression of genes associated with cytotoxic effector functions (GZMA, GZMB, GZMH, PRF1, GNLY, NKG7, and IL-32). We observed the presence of cytotoxic CD4 T cells in COVID-19 patients that were largely absent in healthy volunteers following immunization. While hyperactivation of inflammatory responses and cytotoxic cells may contribute to immunopathology in severe illness, in mild and moderate disease, these features are indicative of protective immune responses and resolution of infection71,105. A multi-cohort analysis of immune responses across different viral infections showed that increased frequency of NK cells and expression of NK-associated genes is inversely correlated with severity106. This is consistent with previous studies that show that reduced NK frequency and function are associated with increased tissue damage and severe COVID-19107.
Our study, together with others, underscores the fine balance between antiviral immune responses that achieve clearance of the infection and durable protective immunity, and those that lead to inflammation and immunopathology. Better understanding of the immunological features associated with protective immunity, immunopathology, and durability of protective immunological memory will aid not only in better treatments for viral diseases, but also facilitate the rapid development of effective vaccines for new and re-emerging viral diseases that threaten public health.
Were I an anti-vaxxer - suspicious of long-term bad effects from anything that interferes with the immune system, I'd take this as obvious evidence (further proved by long COVID) that COVID infection, with its unique interference with the immune system, can deliver long-term damaging results. I'd see COVID as some sort of self-propagating sinister bio-engineered vaccine, and would therefore see vaccination, with a less extreme effect on the immune system, as less harmful. That would create a severe cognitive dissonance.
Since I'm not an anti-vaxxer I cannot draw such a conclusion, except this does underline my strong wish not to catch COVID, or at least not to catch severe COVID (milder versions have less effect on the immune system). If vaccines help with that (as they do) I'm for them.