Limitations of the study include a lack of systematic examination of individual mutations and the potential for mutations to alter neutralization by affecting spike function rather than antigenicity. The onset of protection after one dose of BNT162b2 precedes the development of high neutralizing titers, and BNT162b2 immunization also elicits CD8+ T-cell responses.1,4,5 Thus, it is unclear what effect a reduction in neutralization by approximately two thirds would have on BNT162b2-elicited protection from Covid-19 caused by the B.1.351 lineage of SARS-CoV-2.