Although prior studies have demonstrated reduced neutralizing antibodies against Omicron compared with other variants following receipt of 2 mRNA vaccine doses4,5,7,29,30 (but with potent neutralization following a third dose31,32,33), CD8+ cytotoxic T cells are less affected by sequence variations in the Omicron variant and likely continue to provide protection against severe disease.32,34 Emerging clinical data have demonstrated that vaccine protection is more preserved against severe outcomes than against infection in the Omicron era. This evidence concerns the gene CD8A and infection.