BioNTech SE: An In Vitro Study Shows Pfizer-BioNTech COVID-19 Vaccine Elicits Antibodies that Neutralize SARS-CoV-2 with a Mutation Associated with Rapid Transmission Pfizer Inc.. Rapidly spreading variants of SARS-CoV-2 have been reported, initially in the United Kingdom and South Africa. These variants have multiple mutations in their spike or S glycoproteins, which are key targets of virus neutralizing antibodies. Though these two rapidly spreading viruses are different, they share the N501Y mutation, which is located in the receptor binding site of the spike protein and results in the virus's spike protein binding more tightly to its receptor. It has been shown to infect mice more efficiently.