A new version of the Omicron variant of SARS-CoV-2, known as BA.2, has emerged. Although experts are unsure about its effects, they know that it is spreading quickly and has 20 mutations in the area that most COVID-19 vaccines target.

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Should we be worried about the ‘stealth variant’ of Omicron? Image credit: Kate Geraghty/The Sydney Morning Herald via Getty Images.

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Scientists first identified the BA.2 subvariant of Omicron in India and South Africa in late December 2021. Since then, it has spread to several countries, including the United States, the United Kingdom, and Israel.

The subvariant virus has also spread rapidly in Denmark, increasing from 20% of all COVID-19 cases in the country in week 52 of 2021 to 45% in the second week of 2022.

Despite its rapid spread in the country, initial analyses show no difference in hospitalizations between the BA.2 subvariant and the original form of Omicron, also known as BA.1.

Studies, however, are still ongoing to understand the infectiousness of BA.2, alongside how effective vaccines are against it.

While BA.2 is not currently a “variant of concern,” public health officials in the U.K. have taken enough interest in its spread to designate it as a “variant under investigation.”

To understand more about the emerging subvariant, Medical News Today spoke with six experts in public health, immunology, and infectious diseases.

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“Omicron has three main [subvariants] — BA.1, BA.2, and BA.3 — according to the World Health Organization (WHO),” Dr. Donald C. Vinh, associate professor in the Department of Medicine at McGill University, Canada, told MNT.

“Up until now, the overwhelmingly large majority of all Omicron cases has been BA.1. However, in some places, the BA.2 has emerged and has spread faster than BA.1,” he went on to note.

“This sister variant, which is still Omicron, is interesting because it seems to be displacing Omicron in certain parts of the world,“ Dr. Amesh A. Adalja, senior scholar at Johns Hopkins Center for Health Security, told MNT. “There is speculation that it may be more transmissible than its sibling.”

How the fast spread of the BA.2 subvariant may affect public health is still under investigation.

“The Omicron SARS-CoV-2 variant has been interesting to scientists because of its comparatively (i) higher number of mutations, which […] allow it to partially evade people’s immune response; (ii) higher transmissibility and pathogenicity, i.e., its greater ability to infect and cause disease; and (iii) lower virulence, i.e., its lower ability to cause severe disease,” Dr. Richard Reithinger, Ph.D., vice president of global health at RTI International, explained.

“The big question for newly identified variants and subvariants such as Omicron BA.2 is how these above three characteristics vary from the original SARS-CoV-2 virus [variant] or the Omicron variant and why.”

– Dr. Richard Reithinger, Ph.D.

“If some countries are now reporting a surge in the proportion of BA.2 subvariant infections, is it because the additional mutations make it more transmissible or allow it to evade the immune response more easily than the other Omicron subvariants? Will BA.2 result in the same clinical pathology as the Omicron parent variant (B.1.1.529) and subvariants (BA.1 and BA.3)? Also, how do current therapeutic options and vaccines fare against BA.2?”

According to Dr. Reithinger, these are some of the questions that public health experts must take into consideration while keeping this subvariant under observation.

While researchers are still gathering data on how BA.2 may affect the population at large, laboratory studies have already verified many of its molecular properties.

“BA.2 is missing the spike 69-70 mutations, so it does not cause S gene target failure, making it harder to identify on PCR tests,” Dr. Anna Ssentongo, assistant professor of public health at the Penn State College of Medicine, told MNT.

“Because of this, BA.2 was nicknamed the ‘stealth variant,’” she explained.

Dr. Ssentongo added that BA.2 has more than 20 mutations in its spike protein, which is a target of many COVID-19 vaccines because the virus uses it to enter healthy cells. Although this difference may make BA.2 more resistant to vaccines, further research is necessary to confirm any effects.

“Similar to its parental lineage (Omicron), it is expected to be highly transmissible and result in less severe disease than the Delta or Beta variants, especially if one is fully vaccinated and — even better — boosted,” added Dr. Reithinger. “However, ultimately, this would have to be confirmed by ongoing laboratory and clinical studies, which are expected to provide results in the next couple of weeks.”

Dr. Vinh agreed that before drawing any conclusions on how the subvariant may affect public health, further research is necessary:

“It is important to mention that there are very limited data on clinical differences between BA.2 and BA.1. Specifically, we have no firm data to know if BA.2 is more contagious, results in more severe disease, or can evade immunity better than BA.1. Nonetheless, early data from Denmark and the U.K. suggest that BA.2 may be more contagious than BA.1.”

When MNT asked whether we should be concerned about BA.2, Dr. Pavitra Roychoudhury, research associate at the Vaccine and Infectious Disease Division at the University of Washington, explained: “It remains to be seen how BA.2 will compete against currently circulating viruses […], and also whether it causes more severe disease. […] We will continue to monitor frequencies of BA.2 through the use of genomic surveillance.”

Dr. Adalja agreed that much remains to be seen: “We know that this has been a variant that has been present since the early days of Omicron and that it has some similar and some distinct mutations. It is unclear, as of now, whether it is more transmissible. [It] likely has the same characteristics when it comes to vaccine efficacy and severity.”

“It is too early to know what role [BA.2] may play. It’s likely that it will just be part of the Omicron wave and they extend it over time and eventually become the dominant version of Omicron. More study is needed.”

– Dr. Amesh Adalja

However, Dr. Barton F. Haynes, director of the human vaccine institute in the Department of Medicine at the Duke University School of Medicine, said that due to its molecular changes, there might be cause for concern regarding BA.2.

“We are worried that because it is so different than Omicron BA.1, it may escape current vaccines and Omicron BA.1-neutralizing antibodies,” he noted. “To this point, we are working to study the Omicron BA-2 virus to see whether current vaccine-induced neutralizing antibodies neutralize it.”

“Whether BA.2, or any other Omicron subvariant or other SARS-CoV-2 variant, there is irrefutable evidence that existing vaccines are quite effective in protecting people against infection and highly effective in protecting people from developing severe disease or — worst case scenario — dying upon SARS-CoV-2 infection,” explained Dr. Reithinger.

“Additionally, even if vaccinated, people should consider adhering to nonpharmaceutical interventions, such as face masks, physical distancing, and handwashing, particularly when in crowded and/or high transmission environments,” he advised.

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