What We Know About the ‘Stealth’ BA.2 Omicron Variant

As the Omicron coronavirus surge subsides, researchers are monitoring a highly transmitted sub-variant known as BA.2. While it does not appear to be capable of triggering a new big wave of infections, this option could potentially slow down the current decline in Covid cases and make treatment more difficult.

Here’s what we know about BA.2.

Scientists first discovered the Omicron variant in November, and it quickly became clear that the viral lineage already existed in three genetically distinct varieties. Each branch of Omicron had its own set of unique mutations. At that time, the most common was BA.1, which quickly spread throughout the world. BA.1 was almost entirely responsible for the record spike in cases this winter.

At first, BA.1 was thousand times more common than BA.2. But in early 2022, BA.2 began to show up in most of the new infections.

All versions of Omicron are highly contagious, so this variant quickly supplanted earlier forms of the coronavirus, such as Delta. But a number of studies have shown that BA.2 is even more contagious than BA.1.

IN Denmark for example, researchers have examined the distribution of both subvariants in households. They found that people infected with BA.2 were much more likely to infect people with whom they lived in the same house than people with BA.1. IN England the researchers found that it takes a person with BA.2 less time, on average, to infect another person, which speeds up its spread in communities.

At the beginning of 2022, BA.2 was growing more often in a number of countries. TO February, it became dominant worldwide, displacing the once-dominant BA.1. In the United States, the Centers for Disease Control and Prevention rated that BA.2 jumped to 11 percent in early March from 1 percent in early February. It may soon become dominant in this country as well.

But that doesn’t mean Americans are experiencing a new wave of BA.2 that’s infecting a lot of new people. As BA.2 has become more common in the United States, the total number of new cases has dropped by about 95 percent. Globally, the number of daily new cases has dropped to half that they were at their peak at the end of January.

As many countries relax their defenses against the spread of Covid, they can make it easier for BA.2 to stimulate a new rise in cases. 10th of March report from British researchers suggests that this may be happening there now.

But there are a number of reasons why epidemiologists doubt that BA.2 will cause another massive surge.

One of the most striking features of Omicron was its ability to partially evade vaccine defenses. Breakthrough infections have become more common, helping to push the rise in cases to an all-time high. But vaccines continued to protect people from serious illness, especially those who received boosters. During the Omicron surge, vaccines remained highly efficient against hospitalization.

British health officials compared the effects of vaccines against BA.1 and BA.2 infections. They have found little difference between the two sub-options. In both cases, revaccination provides fairly strong protection against infection and very strong protection against hospitalization.

When Omicron first came out, scientists were amazed at how effectively it could evade immunity caused by infections with earlier variants. That’s because it has mutations that change the surface of the virus, making it hard for antibodies to earlier variants to stick to it.

Because BA.2 carries a number of unique mutations that distinguish it from BA.1, the researchers wondered if it could elude immunity from BA.1 infections. This it doesn’t seem to be. World Health Organization said that BA.1 infection provides strong protection against BA.2 infection.

The Omicron variant turned out to be paradoxical: it was highly contagious, but on average, an individual infection was less likely to lead to a serious case of Covid than infections from the Delta variant. This has resulted in many people getting mild Omicron infections. But that didn’t mean Omicron’s surge was “soft.” Because it has infected many more people than ever before, it has led to a staggering number of hospitalizations and deaths.

Omicron’s research has identified several reasons for its lesser severity. Vaccinations and infections with earlier options have given many people immune protection that keeps Covid from getting out of control. Omicron also appeared to be less dangerous in nature than the other options, causing less lung damage.

Similar experiments are ongoing with BA.2. Japanese researchers who infected hamsters with two variants found that BA.2 causes more severe disease. But it’s not clear how good hamster models are for humans. British explorers found that BA.2 infection is not associated with a higher risk of hospitalization than BA.1.

Like BA.1, BA.2 evasive most FDA-approved monoclonal antibody therapies, rendering them ineffective. Some treatments, such as AstraZeneca’s Evusheld, continue to work. The antivirals Paxlovid, and redeliver remain highly effective against both variants of Omicron when taken shortly after a positive test.

BA.2 was nicknamed the “hidden variant” when BA.2 did not report its presence in positive PCR test samples, making it difficult for investigators to distinguish Omicron cases from Delta and other variant cases. BA.2 carried a mutation that hid one of the three coronavirus control genes that the tests detect.

Now that the vast majority of positive tests are due to Omicron, the missing mutation is irrelevant: almost all viruses found by PCR are BA.1, and those that are not BA.2.

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