The lineages’ rise seems to stem from their ability to infect people who were immune to earlier forms of Omicron and other variants.
Credit: Morteza Nikoubazl/NurPhoto via GettyMere weeks after the variant’s BA.2 lineage caused surges globally, two more Omicron spin-offs are on the rise worldwide. First spotted by scientists in South Africa in April and linked to a subsequent rise in cases there, BA.4 and BA.5 are the newest members of Omicron’s growing family of coronavirus subvariants. They have been detected in dozens of countries worldwide.
Korber and Fischer also found that many genome sequences that are classified as BA.2 in public databases are actually BA.4 or BA.5. As a result, researchers could be underestimating the variants’ ongoing rise, as well as the diversity of mutations carried by them.
On the basis of the rise of BA.5 in Switzerland — where BA.4 prevalence is low — Althaus estimates that about 15% of people there will get infected. But countries are now likely to have distinct immune profiles because their histories of COVID-19 waves and vaccination rates differ, Althaus adds. As a result, the sizes of BA.4 and BA.5 waves will vary from place to place. “It might be 5% in some countries and 30% in others. It all depends on their immunity profile,” he says.