First, there was Delta. Then Omicron. Now, it’s the Omicron subvariant BA.2.12.1. And, public health officials are keeping a close watch on the BA.4 and BA.5 subvariants. These waves of cases, caused by infections with new variants, have characterized the COVID-19 pandemic. But how can public health officials know which variants are likely to cause large numbers of cases and which will not take hold in the population?
