Omicron, BA.2 subvariant, is it the last variant in the pandemic?

Up to date, the COVID pandemic has not been ended due to the high contagious variant, omicron. The omicron variant has been found in four subvariants, BA.1, BA.1.1.529, BA.2, and BA.3 by World Health Organization (WHO). BA.1 is known as the original omicron variant, which was detected in most countries worldwide in early 2022; however, BA.1 is overtaken by BA.2 in Denmark, Nepal, Philippines, United Kingdom…etc. With the emergence of BA.2, BA.3 and Delta variants gradually disappear in most cases. Since researchers predicted that BA.2 will eventually become the dominant variant globally due to its higher transmission, what do we need to know about this subvariant?

Researchers have claimed that subvariant BA.2 is a stealth variant because, in BA.1 subvariant, it loses one of the three target genes we used in a standard PCR, but BA.2 does not. In other words, with a standard PCR test, if the expected result shows the absence of the particular gene, we could conclude that it is omicron, BA.1. But we could not find the same pattern in BA.2 and easily missed spotting this variant. That is why we call it a stealth variant. However, in my opinion, it is not invisible to us, and the only reason we cannot detect it is due to the wrong technique. Also, according to the evolution tree, BA.2 subvariant has been found on a different track than the original omicron subvariant, BA.1. Therefore, scientists have argued whether we need to set Omicron BA.2 as a new COVID variant.

On the other hand, in a report from Denmark, Omicron BA.2 has been found to have a higher transmission rate than BA.1 subvariant because of these different mutations. Additionally, BA.2 subvariant has been the dominant subvariant of COVID-19 in Denmark since January 2022. In the study, scientists collected the data to follow the spreading of Omicron variants within Danish households from December 2021 to January 2022. The result shows that the secondary transfection rates from infected people are 29% and 39% with Omicron BA.1 and BA.2, respectively. This means that BA.2 subvariant could be spread out more quickly than BA.1 subvariant and other COVID variants. In the study, BA.2 subvariant would have a higher possibility for breakthrough infection in fully vaccinated individuals and those with booster vaccination. Also, scientists found that the transmissibility of BA.2 from unvaccinated primary cases is increased when compared to BA.1. Fortunately, researchers did not observe the same pattern in vaccinated individuals. That is, although the BA.2 subvariant could infect fully vaccinated people with and without booster shots, these vaccinated people are less likely to spread the new COVID Omicron BA.2 subvariant. It seems that COVID vaccine could potentially stop the spread of Omicron BA.2 subvariant.

The cumulative COIVD-19 cases by date. The figure was adapted from Johns Hopkins University on 2/9/2022

In the original Omicron variant, BA.1, animal studies and clinical data have shown that BA.1 subvariant is less toxic to humans because it mainly accumulates in the upper respiratory tract and less in the lower respiratory and lung. It means more minor damage to the lung and a lower severity/death rate. And now we are curious that what about subvariant BA.2? Although we do not know the toxicity of BA.2 yet, in the current data, which claimed that Omicron subvariant BA.2 is likely to have the same severity rate as subvariant BA.1. Moreover, at the end of January 2022, Denmark decided to lift all the domestic COVID-19 related restrictions, including wearing masks, despite the increase in COIVD cases. This might indicate that although the omicron variant is more contagious, this virus no longer qualifies as a critical threat to the country with a high vaccination rate. More than 80% of the population has been fully vaccinated in Denmark, and over 60% have received the booster shot. This is excellent news to us to know that the end of the pandemic might be close. However, even though the Omicron variant has a lower severity rate, its high transmissibility might cause the crush of the medical system. For example, the new COVID cases by omicron variant since December 2021 has reached ~20% of the cumulative cases in the United States. This is an alarming number to me. Within 2 months, more than 20 million cases were reported in the United States, and these cases might break down the medical system. In sum, to end the pandemic, please wear a surgical mask (N95 or KN95 are even better.) and get COVID vaccine. With these, I believe that we could have our regular lives soon.

Reference:

  1. Johns Hopkins University, Coronavirus resource center
  2. Meredith Wadman, Scienceinsider 2022 doi: 10.1126/science.ada0810
  3. UK Health Security Agency
  4. Frederik L. et al, “Transmission of SARS-CoV-2 Omicron VOC subvariants BA.1 and BA.2: Evidence from Danish Households”, medRxiv, doi: https://doi.org/10.1101/2022.01.28.22270044 

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