Omicron: The wave we are ready for?

Omicron: The wave we are ready for?


On November 25, 2021 about 23 months since the first reported case of COVID-19 and after a global estimated 260 million cases and 5.2 million deaths, another variant of SARS-CoV-2 was detected in South Africa. It was termed "Omicron" by the World Health Organization (WHO) on November 26, 2021. The introduction of this new variation highlights the necessity of providing the entire nation with access to immunization, maintaining safety standards and establishing a more robust health-care infrastructure. Allowing the virus to freely circulate among non-vaccinated citizens, firstly jeopardizes them with severe COVID-19 cases, which could lead to an increased number of deaths. Secondly, it allows the virus to rapidly generate mutations that could enhance its viral risk of transmission and pathogenicity or lead to new deadly waves across the country and further cause a threat to the world. Thus, it is important to prevent the virus from spreading.

Characteristics of Omicron:

After the first infection, a retrospective review of routine epidemiological monitoring data suggests that the Omicron variant may be associated with an increased risk of reinfection. A SARS-CoV-2 infection was found in 2,796,982 people and 35,670 of those were found to be
reinfected. This finding shows that the Omicron form is capable of evading immunity from past infection.

Omicron has the highest amount of amino acid alterations in the spike glycoprotein, compared to any other species. It is possible that these mutations in Omicron will result in an increased rate of SARS-CoV-2 transmissibility, viral binding affinity and immune escape due to its higher affinity towards the ACE2 receptor of the human body. It is possible that the use of coronavirus-specific attachment inhibitors is not the best option for treating SARS-CoV-2 Omicron at this time because of the heterogeneity in the spike glycoprotein sequences.

Since its discovery, Omicron has been identified in more than 50 countries on six continents. When compared to the previous variants of SARS-CoV-2: Alpha, Beta, Gamma and Delta, Omicron, is found to be the most prominent variant and distinct from the millions of SARS-CoV-2 genomes.

So far, Omicron has been identified as the most divergent SARS-CoV-2 variant, as evidenced by the highest number of amino acid changes discovered in the spike glycoprotein. There is some evidence that these changes in Omicron are associated with increased transmissibility, a much stronger viral binding affinity and immunological escape.

 

Omicron variant and booster COVID-19 vaccines:

According to the Centers for Disease Control and Prevention, the current vaccines are expected to protect against severe illness, hospitalizations and deaths caused by infection with the Omicron strain. Breakthrough infections, on the other hand, are more likely to arise in people who have received all their vaccinations. With other variations, such as Delta, vaccines have maintained their effectiveness in averting serious disease, hospitalization, and even death. The recent development of Omicron serves to highlight the critical significance of vaccination and booster shots even more.

Since vaccine-induced immunity is now well-documented, it is important to receive a booster dosage in order to combat the already continuing and potentially speeding-up increase in cases, regardless of which form of the virus is circulating at any given time. The high frequency of mutations in the spike sequence of the Omicron variation raises concerns about the possibility of this variant escaping the immune system's recognition. The whole combination of mutations identified in the Omicron spike gene has not been explored previously and the significance of these mutations on immunological escape is still being evaluated. Pharmaceutical companies are already evaluating the efficacy of their vaccinations against this new variety in their testing facilities. The population who have been vaccinated or previously infected with different variants of SARS-CoV-2 should undergo in vitro serum neutralisation assays to determine if they are at any risk of being infected by the Omicron variant. Due to the fact that cellular immunity is directed against a variety of viral spike epitopes, we can predict that it will not be as significantly impacted by virus evolution as humoral immunity.

Neutralization by Monoclonal Antibodies:

COVID-19 monoclonal antibody cocktails, such as casirivimab-imdevimab and bamlanivimab-etesevimab, have emerged as important therapeutics for the virus, with demonstrated efficacy in preventing progression to severe disease or hospitalization, as well as in treating severe disease and providing post-exposure prophylaxis in patients. According to the results of in vitro experiments, the Omicron version is totally immune to neutralization by these antibodies.

Omicron was found to be completely or partially resistant to neutralization by all of the monoclonal antibodies tested. An investigation conducted by Planas et al. showed that Omicron was scarcely inhibited by serum from Pfizer or AstraZeneca vaccine recipients, which was collected 5 months following the completion of the vaccination. It was reported that the sera collected after 6 or 12 months from COVID-19 recovering patients had poor or non-existent Omicron neutralizing activity. However, the administration of a booster Pfizer dose, as well as vaccination of previously infected individuals, elicited an Anti-Omicron neutralizing response, with an amount of 6-to-23-fold lower against Omicron as compared to Delta. Vaccination of previously infected individuals also produced an Anti-Omicron neutralizing response. Thus, Omicron is resistant to most therapeutic monoclonal antibodies and to a significant extent, vaccine-elicited antibodies. Omicron on the other hand continues to be neutralized by antibodies produced by a booster vaccine dosage.

Our readiness and alertness:

With the advent of Omicron, it has become an alarming concern that one should remain precautious and adhere to the safety measures, get themselves vaccinated, wear safety masks, avoid large gatherings and maintain distances. A few of the curative methods include social distancing, wearing masks & personal hygiene, which are extremely beneficial and should be followed today and in the future.

Considering the previous experiences with the first and second waves of COVID-19 have led us to believe that only time, strict safety measures implemented at the individual level, surveillance at work and in public gatherings, vaccine accessibility and administration will provide us with the necessary foundation to combat the spread of Omicron. We can already say that protective measures and immunization will continue to be the most important tool in the fight against the spread of the new variant and the prevention of additional outbreaks of severe COVID-19 cases and deaths in the future.

 

References:

  1. https://www.cdc.gov/coronavirus/2019-ncov/variants/omicron-variant.html
  2. https://onlinelibrary.wiley.com/doi/10.1002/jmv.27524
  3. https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC8756165/