If You Have Had the Common Cold, are you Protected From COVID-19 

An interesting article in Science dated 2 October 2020 by Mateus and others suggested that robust T cell responses to SARS-CoV-2 occur in most individuals with COVID-19 disease.  Several studies have reported that some people who had not been exposed to SARS-CoV-2 had pre-existing reactivity to SARS-CoV-2 sequences.  

The immunological mechanisms underlying this pre-existing reactivity are not clear, but previous exposure to widely circulating common cold coronaviruses might be involved.

Mateus Et Al found that the pre-existing reactivity against SARS-CoV-2 comes from memory T cells and that cross reactive T cells can specifically recognise a SARS-CoV-2 epitope as well as the homologous epitope from common cold coronaviruses. 

These findings underline the importance of determining the impacts of pre-existing immune memory in COVID-19 disease severity.