Is Stealth BA.2 Omicron Dangerous? COVID Variant Subtype Spreading in U.S.

The Omicron sub-variant of COVID-19 known as BA.2 appears to be spreading across the United States. But how dangerous is it?

The latest available data from the Centers for Disease Control and Prevention (CDC) suggests that the sub-variant accounts for around a quarter of all new sequenced cases in the United States—and the proportion appears to be increasing.

In fact, if current trends continue, BA.2—informally dubbed "stealth Omicron"—looks set to overtake other types of Omicron in the United States, including the original BA.1 variant.

On Sunday, Anthony Fauci—chief medical adviser to President Joe Biden—told ABC's This Week that BA.2 has a "degree of transmission advantage over the original Omicron [variant], but not a multi-fold advantage."

"It's about 50 percent to 60 percent or so more transmissible, which means ultimately it might take over as a dominant variant. So, it does have an increased transmission capability."

However, Fauci said this potential increase in BA.2 COVID-19 cases would likely not lead to a dangerous surge.

"When you look at the cases, they do not appear to be any more severe and they do not appear to evade immune responses, either from vaccines or prior infection," Fauci said.

Also on Sunday, Dr. Maria Van Kerkhove, the World Health Organization COVID-19 Technical Lead, said at a press conference there is no evidence that BA.2 is any more severe than BA.1.

"However, with huge numbers of cases, you will see an increase in hospitalizations and that in turn has translated into increased deaths, primarily in people not vaxxed or partially vaxxed," she said.

Shangxin Yang, a professor of pathology and laboratory medicine at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA,) said in a statement last week that the difference between BA.1 and BA.2 is extremely small.

"Fundamentally, I don't see much different of BA.1 and BA.2," he said. "There's not even a single bit of evidence that BA.2 is more pathogenic than BA.1. One clear piece of evidence is that despite an increase of cases of BA.2, the death rate continues to decline."

Yang said BA.2 is likely more contagious than the original Omicron variant but probably not by very much.

"BA.2 was actually found when omicron was first noted, in early December, and after more than three months it's still just creeping up to account for about 25 percent of cases. It's taken a long time and it's not even dominant."

According to Yang, there may be a "small" spike in cases of BA.2 in the United States but those primarily affected will probably be individuals who have neither been vaccinated nor exposed to the virus before.

"The vaccine that is effective against BA.1 should be equally effective against BA.2," he said, due to the similarities between the two types.

He added a rise in BA.2 would be "normal" and the we shouldn't be "too concerned" about it.

"For those who are not yet boosted, go get boosted. For those who are not vaccinated, go get vaccinated. If we have a very general practice of behavior, we can do just fine."

"The true issue here is that we're entering a different phase of the pandemic, where the virus has become not as deadly, and we have all the tools we need. We need to now assess whether it's a risk to the general population versus a risk to an individual person."

People wearing face masks in New York
People wear face masks in Times Square on January 25, 2022 in New York City. The Omicron sub-variant of COVID known as BA.2 appears to be spreading across the United States. Noam Galai/Getty Images