The sera neutralized all key mutations in studies conducted by Pfizer and the University of Texas Medical Branch. The results of the study were published on the preprint server bioRxiv and have been submitted to a peer-reviewed journal. In the study, the mutated viruses were tested against a panel of sera from 20 participants in the company's phase III clinical trial. Of the three recombinant variants tested, one has a mutation common to both the U.K. and South Africa variants (N501Y), one has mutations common to the U.K. variant (Δ69/70+N501Y+D614G), and the third has mutations common to the South Africa variant (E484K+N501Y+D614G).

Neutralization of the South African variant was slightly lower compared to neutralization of the other mutations evaluated, but is unlikely to lead to a significant reduction in the effectiveness of the vaccine, according to the companies.

Pfizer and BioNTech will continue to monitor the emerging SAR-CoV-2 strains and continue to conduct studies to monitor the vaccine's real-world effectiveness.