ART4 and infection: This indicates that Omicron BA.1 infection in vaccinated individuals stimulates BMEM cells that produce neutralizing antibodies against S glycoprotein epitopes conserved in the SARS-CoV-2 variants up to and including Omicron BA.2, but that have mostly been lost in BA.4/5 and are for the most part not shared by SARS-CoV-1.