New variants of a virus become dominant through radical mutations that significantly change how the pathogen behaves—and give it a leg-up over its predecessors. With every new variant, there’s a chance it’s changed so much that our antibodies no longer recognize it. “A major genetic shift that would greatly increase its ability to infect humans regardless of vaccination status and prior infections,” according to Alberg.

Epidemiologists call that “immune escape.” It’s the nightmare scenario when it comes to viruses.

Michael modeled the surge of a major immune-escape variant. How bad it gets depends on whether the new variant dodges vaccine-induced antibodies, natural antibodies from past infection or both. “If the immune evasiveness acts similarly on both forms of immunity, then you will get significantly large repeat waves forming depending on the exact rate and strength by which escape occurs,” Michael said.

There are reasons to believe another Omicron sublineage is likeliest to come next. Geneticists scrutinizing viral samples have noted four forms of Omicron vying for dominance in recent weeks. BA.5, of course. But also BA.5.2, BA.2.75 and BA.4.6.