It takes a lot for a COVID-19 variant to become dominant throughout most of the world. It has happened only three previous times (alpha, delta, omicron) and now is occurring with the omicron family subvariant known as BA.5. How did this occur and what are the implications for the pandemic going forward?
In the last weeks BA.5 became the dominant COVID-19 variant in the United States, according to the Centers for Disease Control and Prevention, the cause of nearly 54% of new cases, growing exponentially here since late April. It replaced another omicron family variant (BA.2.12.1), which has not achieved global dominance. But we are seeing BA.5, first appearing in South Africa and Portugal, now progressing to or achieving dominance throughout much of Europe, South America and the Asia Pacific. It has led to new infection surges and an increase in hospitalizations but, fortunately, not a proportionate increase in deaths or admissions to intensive care units.
The reason why BA.5 is a standout is predominantly linked to its property of “immune escape.” That is, multiple distinct mutations from prior omicron variants have blunted our immune response to it. The ability of multiple vaccine doses, boosters and infections to guard against it is reduced.
