The novel coronavirus has a high mortality rate (over 1% for patients older than 50). This could be only partially ascribed to other comorbidities. Possible explanation could be something which assures the ability to prompt response to SARS-CoV-2 in younger people independently from the novelty of the virus itself. Something stimulated the immune system and it scattered immunity against more antigens. The only external stimulation, which healthy people receive, is vaccination (i.e. diphtheria, tetanus, and pertussis (DTP) vaccine). One hypothesis is that vaccination develops the specific immunity but generates a sprouting immunity against antigens in transit. The underlying immunological phenomena are “bystander effect” and “trained immunity”. The developed immunity gives protection for years until the natural fade out. After the fifth decade a viral infection will find immune system almost incompetent and the novel coronavirus bursts into the body, developing an ARDS.
Study of immune-mediated mechanisms in patients tested positive for SARS-CoV-2: phenotypic and functional analysis of monocytes, NK and T cells in the blood of subjects affected by COVID 19
Drug repurposing strategies and key challenges for COVID-19 management