SARS-CoV-2 variants of concern exhibit varying degrees of transmissibility and, in some cases, escape from acquired immunity. Much effort has been devoted to measuring these phenotypes, but understanding their impact on the course of the pandemic—especially that of immune escape—has remained a challenge. Here, we use a mathematical model to simulate the dynamics of wild-type and variant strains of SARS-CoV-2 in the context of vaccine rollout and nonpharmaceutical interventions. We show that variants with enhanced transmissibility frequently increase epidemic severity, whereas those with partial immune escape either fail to spread widely or primarily cause reinfections and breakthrough infections. However, when these phenotypes are combined, a variant can continue spreading even as immunity builds up in the population, limiting the impact of vaccination and exacerbating the epidemic. These findings help explain the trajectories of past and present SARS-CoV-2 variants and may inform variant assessment and response in the future.

值得关注的 SARS-CoV-2 变体表现出不同程度的传播性，在某些情况下，会逃避获得性免疫。人们付出了很多努力来测量这些表型，但了解它们对大流行病程的影响（尤其是免疫逃逸的影响）仍然是一个挑战。在这里，我们使用数学模型来模拟 SARS-CoV-2 野生型和变异株在疫苗推出和非药物干预背景下的动态。我们发现，传播性增强的变异体经常会增加流行病的严重程度，而具有部分免疫逃逸的变异体要么无法广泛传播，要么主要导致再感染和突破性感染。然而，当这些表型结合在一起时，即使人群中免疫力增强，变体也可能继续传播，从而限制了疫苗接种的影响并加剧了流行病。这些发现有助于解释过去和现在的 SARS-CoV-2 变异的轨迹，并可能为未来的变异评估和应对提供信息。