Omicron: What do we know about the ‘stealth variant’?

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.

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date.

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.

Omicron Cases in India: “The current surge of COVID-19 cases in the country is showing a sustained declining trend since January 21, 2022,” said Health Minister Mansukh Mandaviya.

Omicron variant is the dominant variant in the country presently and the current surge of COVID-19 cases in the country is showing a sustained declining trend since January 21, Union Health Minister Mansukh Mandaviya informed the Rajya Sabha on Tuesday.

With the reporting of Omicron, a highly mutated variant of SARSCoV-2 virus and its classification as a Variant of Concern (VoC) by the World Health Organization (WHO), the Union Ministry of Health revised its ‘Guidelines for international arrivals’, Mandaviya said in a written reply.

“Omicron variant is the dominant variant in the country presently. The current surge of COVID-19 cases in the country is showing a sustained declining trend since January 21, 2022,” he said.

Following a risk based approach, provisions for mandatory pre-departure and post arrival RT-PCR testing on day 8th of arrival and a mandatory home quarantine for 7 days have been made in the present guidelines for all international travellers to India.

The Ministry of Health continues to provide technical guidance for managing various aspects of COVID-19 including containment and surveillance, testing, clinical management protocols, post-COVID sequale, etc., the minister said.

The clinical management protocols have also been disseminated under the Ministry of Health’s Center of Excellence initiative for all states in collaboration with AIIMS, Delhi and Indian Medical Association. Besides regular review meetings at the level of Union Health Minister with all relevant stakeholders including subject experts, review meetings with states and UTs through video conferencing have been conducted regularly to review preparedness and response measures to address COVID-19 pandemic, he said.

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.

Rapid spread

“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.

“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.

What we know so far

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:

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