Highly transmissible Omicron subvariant BA.5 has taken over the US: It takes immune escape ‘to the next level’

BA.5 is estimated to have caused nearly 54% of COVID infections in the U.S. last week, according to data from the U.S. Centers for Disease Control and Prevention. Along with twin variant BA.4, it swept South Africa this spring thanks to its ability to evade immunity from both prior infection and vaccination.

The week before that, the two variants combined made up slightly more than half of U.S. cases. But last week, BA.5 accomplished the same feat alone, without the help of BA.4, which came in third...