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The Omicron variant is currently grabbing the headlines. The big question is, should you be worried?

Omicron is Highly Infectious

It is now clear that the Omicron variant is highly infectious and fast becoming the dominant SARS-CoV-2 strain.

The leading hypothesis explaining the emergence of Omicron is that the high number of amino acid changes within the Omicron spike protein allows immune escape, combined with an increased rate of viral entry into host cells (1). These two factors have allowed the Omicron variant to spread rapidly, particularly within vaccinated and naturally immune populations.

A Brief Immune Primer

Your ability to fend off viral infections depends on three factors.

1. Antibodies

Antibodies are proteins created by your immune bind to viruses, thereby preventing viruses from infecting cells. In addition, when antibodies bind to viruses, they target virus particles for destruction by immune cells that gobble up and destroy invading viruses.

1. Cell-mediated Immunity

Your cell-mediated immunity is composed of specialized immune cells called cytotoxic T-cells. Cytotoxic T-cells identify and kill virus-infected cells.

3. Epitopes

The third and final concept to understand is that antibodies and cell-mediated immunity recognize specific amino acid sequences, called epitopes, present within virus proteins.

Neutralizing antibodies recognize and bind to antibody-specific epitopes within virus proteins. In contrast, cytotoxic T-cells recognize and bind to cytotoxic T-cell epitopes present within virus proteins.

The ‘Jab’

The current SARS-CoV-2 vaccines expose your immune system to the SARS-CoV-2 virus spike protein.

We were fortunate with SARS-CoV-2. Because the spike protein is large and contains many epitopes recognized by antibodies and cytotoxic T-cells. Thus, the spike protein is a fantastic target for vaccine development, because it generates both a strong antibody and a strong T-cell mediated immune response, protecting you from serious disease.

Does Omicron Avoid Your Vaccine Antibody Response?

Unfortunately, studies in South Africa revealed that the omicron variant escapes antibodies generated by either a previous natural infection or vaccination (2). Here, the authors estimate that vaccination or previous SARS-CoV-2 infection provides around 35% antibody protection against the new Omicron compared to the original SARS-CoV-2 strain (2).

Moreover, several independent researchers have shown that Omicron avoids antibody-mediated immunity (e.g., see (3-5)), with the estimated reduction in antibody neutralization of Omicron estimated to be around 70-80% (2, 4).

The bottom line is that the Omicron variant avoids the antibody response generated by either vaccine or natural immunity conferred by infection by other SARS-CoV-2 strains. Further, Omicron’s ability to dodge the antibody response allows Omicron to infect people who are vaccinated or naturally immune to earlier variants.

What About Cell-mediated Immunity?

The (really!) good news is that the latest research suggests that the Omicron strain has not escaped cell-mediated immunity (6-9). Importantly, because independent and high-quality laboratories have replicated this crucial finding, we can have high confidence that the result is accurate. Below is a brief overview of some of the critical studies.

First, Drs Ahmed, Quadeer, and McKay revealed that most of Omicron’s T-cell epitopes are unchanged (8). Based on the high preservation of Omicron T-cell epitopes, the Authors predict that for the Omicron variant, ‘the level of protection against severe disease would remain high‘ (8).  

Does this prediction hold true?

If you have natural immunity from a previous SARS-CoV-2 infection, the answer is likely yes.

For example, T-cell response against the Omicron spike protein in 30 patients who recovered from COVID-19 in the USA (6) and South Africa (7) remains strong. Based on this, the authors conclude that ‘virtually all individuals with existing anti-SARS-CoV-2 CD8+ T-cell responses should recognize the Omicron VOC (variant-of-concern)‘ (6).

Next, are the vaccinated also protected from the Omicron strain? Again, the answer is likely yes.

Two independent studies collectively assessed the following vaccines: mRNA vaccines, adenovirus vaccines, combinations of both vaccine types, recombinant protein vaccines, and vaccine and natural SARS-CoV-2 infection (7, 9). Both studies found that vaccinated people retained more than 80% of their cell-mediated immunity against the new Omicron strain. Moreover, all the vaccine and vaccine-infection combinations tested provided very high levels of cell-mediated immunity against Omicron (7, 9).

Thus, your cell-mediated immunity protects you from the Omicron variant if you have natural immunity from a previous SARS-CoV-2 infection (6, 7) or you have been vaccinated (7, 9).

What About People Who Are Unvaccinated and Don’t Have Natural Immunity?

First, two animal studies support the idea that Omicron causes less severe disease than the original SARS-CoV-2 virus. Both Syrian hamsters (10) and mice (11) infected with Omicron showed less severe symptoms, reduced weight loss, and a lower viral load compared to animals infected with the original Wuhan virus strain (10, 11). These two studies suggest that the Omicron variant may cause a less severe infection in humans.

Second, the early stages of the Omicron waves are striking because of the low levels of death compared to a large number of infections (for example, see Figure 1). However, a crucial factor to consider is that many societies (e.g., the USA, the UK, and South Africa) have reached high levels of herd immunity through a combination of vaccination and natural infection. Thus, it’s currently unclear whether the low mortality associated with Omicron is due to herd immunity (in the form of cell-mediated immunity), a less deadly virus, better COVID-19 treatments within the hospital setting, or a combination of these factors.

the Omicron variant is highly infectious and fast becoming the dominant SARS-CoV-2 strain
Figure 1. Rates of SARS-CoV-2 infection, deaths, and hospitalizations in New York State. Image obtained from the Johns Hopkins Coronavirus Resource Center

Third, there is presently no data on the long-term health consequences of Omicron infection. Although death rates for Omicron are (currently) low, note that hospitalization rates have significantly increased (Figure 1). Thus, if your Omicron infection is severe enough to warrant hospitalization, you face an increased risk of the virus spreading throughout your body and causing organ damage due to viral infection and subsequent inflammation.

In my opinion, vaccination is the way to go, because it prevents the SARS-CoV-2 virus from spreading throughout your body. However, if you choose to forgo vaccination, I highly recommend that you read our articles on boosting your natural immune system.

Take-Home Message

It’s now clear that the vaccinated and those with natural immunity are susceptible to Omicron infection, driving the current surge in SARS-CoV-2 infections across the globe.

Fortunately, Omicron remains vulnerable to cell-mediated immunity induced by (i) vaccination, (ii) a previous SARS-CoV-2 infection, or (iii) a combination of both, which explains why the Omicron strain isn’t causing widespread death within immune populations.

So, should Omicron worry you? Not if you are vaccinated or have natural immunity from a previous SARS-CoV-2 infection.

Omicron remains vulnerable to cell-mediated immunity

References and Further Reading

1.            X. Zhang et al., SARS-CoV-2 Omicron strain exhibits potent capabilities for immune evasion and viral entrance. Signal Transduct Target Ther 6, 430 (2021).

2.            S. Cele et al., SARS-CoV-2 Omicron has extensive but incomplete escape of Pfizer BNT162b2 elicited neutralization and requires ACE2 for infection. medRxiv,  (2021).

3.            W. F. Garcia-Beltran et al., mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against SARS-CoV-2 Omicron variant. Cell,  (2021).

4.            L. Lu et al., Neutralization of SARS-CoV-2 Omicron variant by sera from BNT162b2 or Coronavac vaccine recipients. medRxiv,  (2021).

5.            L. Liu et al., Striking Antibody Evasion Manifested by the Omicron Variant of SARS-CoV-2. bioRxiv, 2021.2012.2014.472719 (2021).

6.            A. D. Redd et al., Minimal cross-over between mutations associated with Omicron variant of SARS-CoV-2 and CD8+ T cell epitopes identified in COVID-19 convalescent individuals. bioRxiv,  (2021).

7.            R. Keeton et al., SARS-CoV-2 spike T cell responses induced upon vaccination or infection remain robust against Omicron bioRxiv, 2021.12.26.21268380 (2021).

8.            S. F. Ahmed, A. A. Quadeer, M. R. McKay, SARS-CoV-2 T cell responses are expected to remain robust against Omicron. bioRxiv, 2021.2012.2012.472315 (2021).

9.            L. De Marco et al., Preserved T cell reactivity to the SARS-CoV-2 Omicron variant indicates continued protection in vaccinated individuals. bioRxiv, 2021.12.30.474453 (2021).

10.          K. A. Ryan et al., Convalescence from prototype SARS-CoV-2 protects Syrian hamsters from disease caused by the Omicron variant. bioRxiv, 2021.2012.2024.474081 (2021).

11.          E. G. Bentley et al., SARS-CoV-2 Omicron-B.1.1.529 Variant leads to less severe disease than Pango B and Delta variants strains in a mouse model of severe COVID-19. bioRxiv, 2021.2012.2026.474085 (2021).

Acknowledgements

Image provided by JONGHO SHIN

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Disrupted sleep increases anxiety and depression. Yoga Nidra is an effective method that has helped many people overcome insomnia.

Beautiful Woman Running On Treadmill

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Emerging research shows that low-intensity cardio is the best way to improve your metabolic and cardiovascular health.

Strong bones, strong brain.

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