It's been one year since the omicron variant was first discovered in South Africa and went on to cause massive Covid-19 surges around the world. Since then, omicron has rapidly evolved into hundreds of subvariants, many of which are more transmissible and better at evading immunity, Carl Zimmer writes for the New York Times.

Omicron continues to evolve rapidly even a year later

Last Thanksgiving, scientists in South Africa announced the discovery of a new coronavirus variant, B.1.1.529, after the country saw a rapid rise in Covid-19 cases over several weeks. On Nov. 26, 2021, the World Health Organization officially named the new variant omicron and designated it a "variant of concern."

Compared to prior coronavirus variants, omicron had more than 50 different mutations, which helped it quickly surge to dominance around the world in the weeks after its discovery. According to Zimmer, some of these mutations allowed omicron "to slip inside cells more successfully" or "evade some of the antibodies from vaccines or previous infections."

Since then, omicron has evolved rapidly, with new subvariants emerging "like a series of waves crashing on a beach," Zimmer writes. Overall, there have been hundreds of different omicron subvariants, including BA.1, BA.2, and BA.5. Currently, BQ.1 and BQ.1.1 are the two dominant subvariants in the United States.

Because there are so many different versions of omicron, "[i]t's hard to remember what is what," said Jesse Bloom, a virologist at the Fred Hutchinson Cancer Center.

However, unless a substantially different coronavirus variant emerges, people will likely have to deal with "this confusing jumble of [omicron] subvariants" for a while, Zimmer writes.

"It's always going to kind of be like it is now," Bloom said. "There's always going to be some soup of new variants out there."

Omicron continues to rack up new mutations. In a process called "convergence," many of these new subvariants are independently gaining similar mutations that allow them to spread more rapidly or evade antibodies more easily.

"The evolution that's happening is the fastest rate it has been up to this point," said Sergei Pond, a virologist at Temple University.

How this rapid evolution could affect Covid-19 treatments

As the different omicron subvariants continue to mutate, they will likely gain more and more resistance to different antibodies.

Yunlong Cao, a biochemist at Peking University, and his colleagues recently reported that four omicron subvariants, including XBB, which is dominant in Singapore, have become entirely resistant to antibodies found in blood samples of individuals who were either vaccinated or previously infected.

Already, this growing resistance from different omicron subvariants has impacted the effectiveness of different monoclonal antibodies, including AstraZeneca's Evusheld and Eli Lilly's bebtelovimab.

"I can't really be confident whether or not monoclonal antibodies will play a major role in treatment going forward," Bloom said. "It's going to be really important to design another generation of antibody cocktails that hopefully stand up longer."

In addition, while research suggests that the updated bivalent boosters are more effective at neutralizing BQ.1.1 and other omicron subvariants than the original vaccines, these subvariants can still evade many antibodies produced by the updated boosters.

However, the new omicron subvariants do not appear to be more deadly than previous versions, and Theodora Hatziioannou, a virologist at Rockefeller University, said it's unlikely they'll be able to escape immunity from vaccines or prior infections entirely.

In addition, Moritz Gerstung, a computational biologist at the German Cancer Research Center in Heidelberg, said that what scientists are learning now about omicron's convergent evolution may allow them to predict its evolution in the future, which could then allow public health officials to prepare for new variants more effectively.

"It has made me very hopeful for the future as a paradigm," Gerstung said. "It's an instance of how one could basically get ahead of the game." (Zimmer, New York Times, 11/26)