SARSCoV2 reactive CD4 T cell response have been identified in unexposed humans. THIS IS DIRECT evidence that pre-existing immune memory can be derived from exposure to common cold coronaviruses. This is an absolute game changer!

It's uncertain how long t-cell mediated immunity for HCOV viruses lasts or how long ago those showing this cross immunity actually had a cold caused by a HCOV virus since we simply don't tend to test most who have colds. However, the issue is these HCOV coronaviruses are great at adapting and evolving so are able to continually infect humans https://www.nature.com/articles/s41467-017-01706-x

But if the t-cell memory of these coronaviruses gives cross protection for this coronavirus, despite them being able to reinfect us at some point themselves, then that's great. Sure children and adults being isolated (that's the main issue not masks which aren't actually supported by high level evidence as being effective) is a major problem but that doesn't mean all is lost.

/r/LockdownSkepticism Thread Parent Link - science.sciencemag.org