[Editor: the following is a bit sciency but is well worth the study.]
1) Antibody studies ⇓2) Immunology ⇓3) Median age of death ⇓4) Hospitalizations ⇓5) Nursing homes ⇓6) Overall mortality ⇓7) Influenza comparison ⇓8) Seroprevalence per country ⇓
1) Antibody studies
The covid infection fatality rate (IFR) depends on demographics (age and risk structure), public policies (e.g. protection of care homes), and medical treatment quality. In most Western countries, the median age of covid deaths is 80+ years and about 50% of deaths occurred in care homes (s.b.)
For comparison, the IFR of seasonal influenza, against which prior immunity and vaccines exist, is about 0.05% to 0.1%; the IFR of epidemic and medium pandemic influenza, such as in 1936, 1951, 1957 and 1968, is about 0.3%; the IFR of the 1918 pandemic influenza was about 2%. (Source)
In terms of covid-19 IFRs, an important difference exists between places with and without a partial or total collapse of local health and elderly care, and between the early and late pandemic phase. In the following table, NNH refers to the non-nursing home population (see section 5).