Det är pga T-cellerna och tidigare infektion av säsongscoronavirus som gör att man dör av covid-19 :
https://www.nature.com/articles/s41467-021-24938-4
SARS-CoV-2 infection of children leads to a mild illness and the immunological differences with adults are unclear. Here, we report SARS-CoV-2 specific T cell responses in infected adults and children and find that the acute and memory CD4+ T cell responses to structural SARS-CoV-2 proteins increase with age, whereas CD8+ T cell responses increase with time post-infection.
Infected children have lower CD4+ and CD8+ T cell responses to SARS-CoV-2 structural and ORF1ab proteins when compared with infected adults, comparable T cell polyfunctionality and reduced CD4+ T cell effector memory. Compared with adults,
children have lower levels of antibodies to β-coronaviruses, indicating differing baseline immunity. Total T follicular helper responses are increased, whilst monocyte numbers are reduced, indicating rapid adaptive co-ordination of the T and B cell responses and differing levels of inflammation.
Therefore, reduced prior β-coronavirus immunity and reduced T cell activation in children might drive milder COVID-19 pathogenesis.
https://www.sciencedaily.com/releases/2021/07/210727104711.htm
New research conducted in monkeys reveals that T cells are not critical for the recovery of primates from acute COVID-19 infections. T cell depletion does not induce severe disease, and T cells do not account for the natural resistance of rhesus macaques to severe COVID-19. Furthermore, strongly T cell-depleted macaques still develop potent memory responses to a second infection.
För ett år sedan skröt Karolinska om att de hittat T-cells immunitet, deras slutsats var fullständigt fel:
https://news.ki.se/immunity-to-covid-19-is-probably-higher-than-tests-have-shown
A new study from Karolinska Institutet and Karolinska University Hospital shows that many people with mild or asymptomatic COVID-19 demonstrate so-called T-cell-mediated immunity to the new coronavirus, even if they have not tested positively for antibodies.