Introduction. The emergence of SARS-CoV-2 Variants of Concern (VOC) and Variants of Interest (VOI) underlies an urgent requirement to define robust measures of protective immunity that can be utilized to triage at-risk populations and effectively target preventative countermeasures1,2,3,4,5. The Pfizer/BioNTech mRNA vaccine BNT162b2 is a leading vaccine approved by the US Food and Drugs Agency (FDA). However, there remains a significant concern about the degree of cross-protection afforded...