Quantifying the Potential Dominance of Immune-Evading SARS-CoV-2 Variants in the United States

Recent evidence suggests that the SARS-CoV-2 variant B.1.351 exhibits partial immune evasion to antibodies generated by natural infection or vaccination. We used a dynamic transmission model to evaluate whether this variant could become dominant in the United States given mounting vaccination coverage and other circulating variants. In the presence of the B.1.1.7 variant, we show that B.1.351 is unlikely to become dominant even when all fully vaccinated individuals return to their pre-pandemic behavior. However, an improved selection advantage of B.1.351 arising from a combination of increased transmission and immune escape could drive this variant to dominance as early as July 2021 and fuel a resurgence of cases and hospitalizations. Our study underscores the urgency for continued rollout of the current generation of vaccines despite the emergence of immune escape variants.