These data suggest that virtually all individuals with existing anti-SARS-CoV-2 CD8+ T-cell responses should recognize the Omicron VOC, and that SARS-CoV-2 has not evolved extensive T-cell escape mutations at this time.
http://archive.today/2021.12.12-062920/https://www.biorxiv.org/content/10.1101/2021.12.06.471446v1