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What do we know about the BA.2 variant?


by Health DeskPublished on March 23, 2022

What our experts say

The BA.2 variant is a version of COVID-19's very contagious Omicron variant, known officially as B.1.1.529. The earliest Omicron subvariant to be detected was BA.1, which is what caused a 2021-2022 COVID-19 surge in many parts of the world at the end of 2021 and beginning of 2022. BA.2 shares around 30 mutations with BA.1, which is why it is considered a subvariant of Omicron rather than a completely new variant.

When it comes to understanding how severe a variant is, there are three questions that need to be asked:

  1. Is it more transmissible than past variants?
  2. How well does it evade immunity, meaning how good is it at infecting people who already had COVID-19 or received a COVID-19 vaccine?
  3. Does it cause more severe disease than past variants?

Overall, current research shows that BA.2 has something called a "growth advantage" over BA.1. That means it is easier for the subvariant to spread. Research is ongoing to understand what contributes to this growth advantage, but current data suggest that BA.2 appears to be somewhere between 30% - 50% more transmissible than BA.1.

Early data also shows that BA.2 is better at infecting people who have immunity to COVID-19 from vaccines or previous infections. Research are still testing just how much natural and vaccine-related protection people might have against BA.2.

Thankfully, BA.2 does not appear to cause more severe cases of COVID-19. Severity of disease is currently predicted to be the same as BA.1. In addition, current data shows that having been infected with BA.1 (the original Omicron variant) offers strong protection against a reinfection with BA.2.

So far, the BA.2 subvariant has not yet been declared a variant of concern on its own, but is considered a variant of concern under the parent variant Omicron. It's likely that the latest global surges in COVID-19 cases are at least partially because of BA.2. But there are other factors at play. For one, many countries have relaxed COVID-19 protection measures in the past 1 - 2 months, making some people more vulnerable to infection. In addition, if people received boosters a few months ago, the efficacy of those shots may now be waning.

Experts do not currently expect a large surge of COVID-19 cases in the U.S., but predict a possible small surge if measures continue to relax and behaviors continue to be more risky. This prediction is based on a few factors such as modeling, timing, and wastewater monitoring, which can act as an early predictor of COVID-19 trends in the near future. Individuals who monitor wastewater say that there's not currently evidence of a wave in the U.S. wastewater data at this time (late March). During the first Omicron wave (BA.1) in December, the level of the virus in wastewater was rising about 100 times faster than it is now.

In addition, because the BA.1 variant infected so many people around the world, it is likely that a large portion of the population has protection against BA.2.

Context and background

Some virus variants can help the virus spread easily from one person to another. Some may cause more severe symptoms.

Subvariant BA.2 is one of the variants that is successful at helping the virus transmit easily from one person to another. That is why there are many cases of it, and why the number of BA.2 cases is still growing.

There is concern about what BA.2’s spread means for the health of populations around the world, and questions about how large the surge might become. Research is ongoing to answer these questions and make sure the public is as protected as possible from COVID-19 infection.

Used with Permission from Health Desk, a public health hub that explains emerging COVID-19 science.

This article was written and edited by the Tayo editorial desk and has been reviewed by an independent panel of subject matter experts.

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