Studies on Covid-19 lethality
Last updated: September 9, 2020; First published: May 12, 2020
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Overview: 1) Immunological studies; 2) Antibody studies; 3) Median age of death; 4) Hospitalization rate; 5) Nursing homes; 6) Overall mortality; 7) Development; IFR: Infection fatality rate.

1) Immunological studies

Immunological research indicates that serological antibody studies, which measure antibodies in the blood (mostly IgG) and typically found IFR values between 0.1% and 0.5% in the general population (see below), may detect only about 20% to 80% of all coronavirus infections. 

This is because up to 80% of people develop no symptoms or only mild symptoms if infected, as they neutralize the coronavirus with their mucosal (IgA) or cellular (T-cells) immune system. These people may develop no measurable IgG antibodies or may show them only for a few weeks.

Most global Covid-19 hotspots peaked at about 20% IgG antibody prevalence (e.g. New York City, London, Stockholm, Madrid, Bergamo). Moreover, among people with anosmia (temporary loss of the sense of taste or smell) – a very typical Covid-19 symptom – only about 20% to 50% had detectable IgG antibodies, according to surveys in several countries (see below).
— Lees op swprs.org/studies-on-covid-19-lethality/