Understanding COVID-19 & SARS-CoV-2 Variants

Over the past few years following the COVID-19 pandemic, you may have heard of terms like variants, subvariants, Alpha, Beta, Delta, Omicron, or more recently, Arcturus, Eris and Pirola. But do you know what they mean and how they can help us understand the virus and mitigate the pandemic?

What are variants?

Viruses tend to evolve as they spread between people. This is due to changes in the genetic code that occur during the genome replication, which can be caused by genetic mutations or viral recombination.

Most genetic changes do not affect the properties of the virus. However, some changes may alter certain critical properties, such as the rate of transmission, the severity of disease symptoms, the viral evasion of vaccines and the resistance built against medicines. When a virus undergoes significant changes due to one or more mutations that make it different from the original virus, it is known as a ‘variant’.

Varieties of variants

During the pandemic, SARS-CoV-2 variants with shared attributes and characteristics can be classified into these categories based on their evaluated risks:

  • Variants under monitoring (VUM): A variant with genetic changes that are suspected to affect viral features, showing early indicators of growth advantage relative to other circulating variants, but the evidence of its impact on a larger scale remains unclear, and enhanced monitoring and reassessment with new evidence are required.
  • Variants of interest (VOI): A variant with genetic changes that are predicted or known to affect viral features (e.g. transmissibility, virulence, antibody evasion, susceptibility to therapeutics) and known to have a growth advantage over other circulating variants in multiple regions, with increasing prevalence and number of cases over time or other impacts that suggest a growing risk to global public health.
  • Variants of concern (VOC): A variant that meets the definition of a VOI and fulfils at least one of the following criteria when compared with other variants:
    • Significant increase in disease severity
    • Change in COVID-19 epidemiology that severely affect the ability of health systems to provide care to patients, thus requiring major public health interventions
    • Significant decrease in vaccine effectiveness against severe disease

Throughout the COVID-19 pandemic, SARS-CoV-2 has continued to mutate and many variants have been identified globally. In May 2021, the World Health Organization (WHO) began assigning labels using Greek letters to both VOC and VOI to make it easier for the public to discuss and refer to significant SARS-CoV-2 variants.

Here are some of the key variants:

  • Alpha (B.1.1.7): It was the first highly publicised variant labelled using Greek letters. The variant was first reported in the United Kingdom in November 2020. Studies suggested that the variant was 40-80% more transmissible than the original virus. It was the predominant variant before the rise of the more aggressive Delta variant.
  • Delta (B.1.617.2): This variant was first detected in India in October 2020. It became the predominant variant until Omicron took its place in mid-December 2021. Studies estimated that Delta caused more than twice as many infections as previous variants.
  • Omicron (B.1.1.529) and subvariants: The original Omicron variant was first detected in Botswana and reported in South Africa in November 2021. The variant quickly began to appear and multiply in other countries, making it the predominant circulating variant globally by the end of 2021. In 2022 and 2023, it generated several subvariants, e.g. BA.2.75 (nicknamed “Centaurus”), 1.16 (nickname “Arcturus”), EG.5 (nicknamed “Eris”) and BA.2.86 (nicknamed “Pirola”). The Omicron variants account for over 98% of the publicly available sequences since February 2022, thus new SARS-CoV-2 variants will likely emerge from these variants.

Variants and vaccination

The diversity of SARS-CoV-2 variants complicates our effort in controlling COVID-19, even though multiple vaccines have been produced and distributed around the world. According to studies, some variants are more resistant to the vaccines and can evade the immune response. This could be a possible explanation for how reinfection can occur in people who have recovered from COVID-19 or have been vaccinated.

Even with the emergence of new variants, the good news is vaccinations can still protect us from the worse consequences of COVID-19. The currently available vaccines are expected to provide at least some protection against new variants because vaccines are typically created to produce a broad immune response. Hence, changes in the viral genome should not make vaccines entirely ineffective. It is also possible to modify the vaccine composition to protect against these newer variants. Scientists, researchers and health officials are also working together to understand how these variants influence the traits of the virus and the vaccine effectiveness, and how the vaccine can be improved and updated.

In the meantime, prevention is still the best protection against COVID-19. Apart from the standard preventive measures like good hygiene and respiratory etiquette, a booster dose is recommended for high-risk groups 6-12 months after the previous dose. Up-to-date vaccination, including booster doses, can reduce the risk of severe illness, hospitalisation, and death. Consult your healthcare provider to learn more about the COVID-19 booster dose and how you can get it.

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