Omicron Variant: BA.2 Sublineage

By Hannah Morpurgo and Julia Schurr

According to the World Health Organization, by February 19, 2022, BA.2 had been detected in 74 countries and 47 US states. BA.2 is a subvariant of Omicron which, according to studies from the UK and Denmark, is 30% more transmissible than BA.1. Although Covid-19 cases have altogether been decreasing, the number of BA.2 cases have been on the rise. The BA.2 variant is now responsible for every 1 in 5 Covid-19 cases worldwide.

Current symptoms include:

• Fever
• Body aches
• SpO2 level dropping
• Omicron-like symptoms

As with any strain thus far, scientists have not hesitated to begin studying the severity of BA.2. However, with relatively few cases due to its recent emergence, results are not yet considered generalizable.

BA.2 vs. BA.1

One study conducted by Beth Israel Deaconess Medical Center (BIDMC) explored the ability of BA.2 to evade antibodies from vaccines or BA.1 immunity. The results indicated that BA.2 behaved similarly to BA.1 in its ability to evade present immunity, although it generated slightly less antibodies. The authors concluded that this was encouraging because it suggested that the increased prevalence of BA.2 is likely due to greater transmission ability rather than its ability to avoid antibodies more efficiently than BA.1.

South Africa

November 17, 2021 was the date of the first detection of the BA.2 sub-lineage in South Africa. By December 5, 2021, BA.2 prevalence had increased, growing up to 84% of the cases amongst the samples used in the study by February 5, 2022. The study assessed risk factors for hospitalization and severe disease. The authors found the odds of being hospitalized were not significantly different between individuals with the BA.2 infection compared to the BA.1 variant infection. The data also suggested that severe disease did not differ between those with BA.1 compared to those with BA.2 infection. As with most studies at this time, one of its limitations was the small sample size.

Pulmonary Risk

An additional study found that BA.2 is able to copy itself at a faster rate than BA.1 and is more inclined to form clumps of cells called syncytia. These syncytia were common to the delta strain and may pose a greater threat to the lungs than the BA.1 variant did. Despite the seemingly more pathogenic and contagious nature of BA.2, scientists do not currently think there is a reason to panic because of the immunity many have from recent infections, vaccines, boosters, or a combination.

Vaccine Resistance

Similar to the BA.1 subvariant, BA.2 has also been documented to escape vaccine immunity, However, a booster shot restores the immunity generated by vaccines against BA.2 by about 74%. A different study has also suggested that the BA.2 subvariant is resistant to sotrovimab, which has been the most recommended treatment against omicron. One thing scientists find promising is that recent infection from the BA.1 variant provides protection against BA.2, to a larger extent if they’d also been vaccinated.

Moving Forward

The BA.2 subvariant is particularly distinctive in that it neglects to show up on PCR tests in the same way that BA.1 does; labs must undergo additional testing in order to identify the variant. One of the next steps in controlling the spread of the BA.2 variant is establishing a testing procedure to effectively isolate and detect it.

References

Goodman, Brenda. “As Ba.2 Subvariant of Omicron Rises, Lab Studies Point to Signs of Severity.” CNN, Cable News Network, 19 Feb. 2022, https://www.cnn.com/2022/02/17/health/ba-2-covid-severity/index.html.

Goodman, Brenda. “New Studies Bring Ba.2 Variant into Sharper Focus.” CNN, Cable News Network, 24 Feb. 2022, https://www.cnn.com/2022/02/23/health/covid-ba2-omicron-studies-explainer/index.html.

Goshwami, Sarmistha, et al. “Omicron Ba.2 Variant Symptoms, Severity, Precautions, Mutation.” DMER Haryana: Recruitment, News, Admit Card, Result, 28 Feb. 2022, https://dmerharyana.org/omicron-ba-2/.

“Omicron Subvariant: Do Covid Treatments Work against BA.2? Scientists Keep Close Watch.” NBCNews.com, NBCUniversal News Group, 18 Feb. 2022, https://www.nbcnews.com/health/health-news/omicron-subvariant-covid-treatments-work-ba2-scientists-keep-close-wat-rcna16836.

Wolter, Nicole, et al. “Clinical Severity of Omicron Sub-Lineage BA.2 Compared to Ba.1 in South Africa.” MedRxiv, Cold Spring Harbor Laboratory Press, 1 Jan. 2022, https://www.medrxiv.org/content/10.1101/2022.02.17.22271030v1.full.