The BA.2 sublineage of Omicron remains "a variant of concern," in the opinion of one of the world's leading health agencies.
The World Health Organization, part of the United Nations, announced on Tuesday that scientists are still in the early stages of assessing the Covid-19 variant. The BA.2 variant seems more transmissible, the agency states:
Studies are ongoing to understand the reasons for this growth advantage, but initial data suggest that BA.2 appears inherently more transmissible than BA.1, which currently remains the most common Omicron sublineage reported.
That news comes as health authorities worldwide seek to understand what this new variant means for the future of the pandemic, which has killed an estimated 5.91 million people worldwide. More than 428 million cases of Covid-19 have also been reported.
The Omicron wave, which reached its global peak roughly one month ago, in January 2022, shattered all previous records for the number of new Covid-19 cases. Today, nearly all cases worldwide are due to one of the Omicron variants. BA.1 remains the most common sublineage, but authorities are worried by evidence that shows BA.2 gaining ground.
Spike protein mutations seem to make BA.2 a more transmissible form of Omicron
While reliable data are still emerging, the WHO says the difference between BA.2 and BA.1 is far less significant than between the Delta variant and the original BA.1 Omicron variant.
Most of that data comes from countries where variant has taken hold, such as Denmark
Brunei, Georgia, Nepal, and the Philippines. Denmark, for example, registered hardly any cases of BA.2 in mid-December. Two months later, the subvariant accounts for roughly 90 percent of new cases in the country.
Three weeks ago, the variant was causing 1.0 percent of cases in the U.S. By last week, that number had nearly quadrupled to 3.8 percent.
The rapid rate of growth has experts “on the edge of our seats.”
Samuel Scarpino, a researcher tracking the spread of the Covid-19 for the Rockefeller Institute, says the rapid rate of growth has experts like him "on the edge of our seats."
"If it doubles again to eight percent, that means we're into the exponential growth phase, and we may be staring at another wave of Covid-19 coming in the U.S.," he says.
Early evidence suggests immunity and vaccines offer protection from BA.2
The news from the WHO provides reassurance that another wave isn't likely. While there are reports of BA.2 managing to evade antibodies from an earlier bout with BA.1, such repeat infections are uncommon.
"[I]nitial data from population-level reinfection studies suggest that infection with BA.1 provides strong protection against reinfection," the organization says.
While epidemiological data about how well natural immunity and vaccines protect against BA.2 remains elusive, laboratory studies suggest the new variant is only slightly better equipped to overcome those forms of protection than BA.1.
"Our data would suggest that [BA.2] would not lead to a brand-new additional surge.”
The author of one of those studies, immunologist, and virologist Dan Barouch, said earlier this month that BA.2 "might prolong the Omicron surge. But our data would suggest that it would not lead to a brand-new additional surge."
Monoclonal antibody treatments are less effective against BA.2
BA.2 does pose a significantly higher risk to infected people. That's because the new subvariant is resistant to some of the most effective tools doctors have in fighting Covid-19 infections. According to a handful of studies, some monoclonal-antibody therapies, which use factory-made immune molecules to help patients respond to infection, are far less effective against the new variant.
The original Omicron variant has already rendered many such treatments far less effective. Sotrovimab, one of the few monoclonal-antibody therapies that remained useful through the Omicron wave, seems far less useful against BA.2.
The problem is that monoclonal-antibodies are designed to anchor onto the virus's now-famous spike protein. Unfortunately, that's the part of the virus where mutations are happening most rapidly. The Omicron variant has been effective because dozens of mutations caused the spike protein to change significantly.
Researchers developing and tweaking monoclonal-antibodies are struggling to keep up.
"With monoclonal antibodies, we're trying to hit a moving target," says virologist David Ho, a co-author on a study that documented the treatment's waning effectiveness. "It's a really difficult [endeavor] to chase after a virus."