Immunity & Herd Immunity

Since our bodies had to deal and were already in contact with different variants of coronaviruses in the past, it appears that most people already have a congenital, general or cross-immunity to e.g. influenza and other viruses.

Immunity to COVID-19 is probably higher than tests have shown

SARS-CoV-2 T-cell epitopes define heterologous and COVID-19-induced T-cell recognition
New German study confirms that 81% of pre-Covid blood donors show T-cell reaction against SARS-CoV-2. This Confirms that ~19% of people are only expected to be infected with Covid19!

SARS-CoV-2-specific peptides enabled detection of post-infectious T cell immunity, even in seronegative convalescent individuals. Cross-reactive SARS-CoV-2 peptides revealed pre-existing T cell responses in 81% of unexposed individuals and validated similarity with common cold coronaviruses, providing a functional basis for heterologous immunity in SARS-CoV-2 infection.

Published: 30 September 2020

Targets of T Cell Responses to SARS-CoV-2 Coronavirus in Humans with COVID-19 Disease and Unexposed Individuals
Importantly, we detected SARS-CoV-2-reactive CD4+ T cells in ∼40%–60% of unexposed individuals, suggesting cross-reactive T cell recognition between circulating “common cold” coronaviruses and SARS-CoV-2.

Diagnosis and Tracking of Past SARS-CoV-2 Infection in a Large Study of Vo’, Italy Through T-Cell Receptor Sequencing

We analyzed T-cell and antibody signatures in a large population study of over 2,200 individuals from the municipality of Vo’, Italy, including 70 PCR-confirmed SARS-CoV-2 cases (24 asymptomatic, 37 symptomatic, 9 hospitalized). Blood samples taken 60 days after PCR diagnosis demonstrated 97% (68/70) of the latter subjects had a positive T-cell test result, higher than an antibody serology assay (77%; 54/70 of subjects) performed on the same samples.

WHO changed the definition of herd immunity.
2019 definition and 2020 definition.

WHO changed definition of Immunity

Please also check our Basics page about our immune system.

All information is deemed accurate but not guaranteed and should be independently verified.