Since BNT162b2, mRNA-1273 and Ad26.COV2.S were each designed to elicit an Ig response against CoV2 Spike (since it is essential for CoV2 infection of ACE2-expressing cells), we assessed whether breakthrough infections with CoV2Delta were associated with lower levels of Spike-specific Ig in saliva compared to PCR (neg) vaccinees. This evidence concerns the gene ACE2 and infection.