Tue, Jun 21, 2022 page8

• Next variant impossible to predict

  • By Ian Hsu 許英昌
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  The WHO in November last year gave the name “Omicron” to a newly discovered strain of SARS-CoV-2, first detected in South Africa.

  Taken together with other variants of the virus, Alpha, Beta, Gamma and Delta, five major SARS-CoV-2 variants have been detected globally.

  Of these, the scientific community is paying the greatest attention to Omicron. The original Omicron strain, B.1.1.529, evolved into subvariants BA.1, BA.2.12.1 and BA.3 — and most recently, the BA.4 and BA.5 subvariants have emerged.

  It is Omicron BA.2 that is presently sweeping through Taiwan.

  What do we know about SARS-CoV-2 and Omicron?

  There were nine mutations on the spike protein of the Alpha variant. Mutation N501Y increases the ability of the receptor-binding domain (RBD) on the spike protein to bind with the ACE2 receptor on the surface of host cells, causing a 50 percent increase in the infection rate over the original strain of SARS-CoV-2.

  The Beta variant contains 10 mutations to the RBD. Mutation E484K makes it more difficult for antibodies to block the virus.

  The Gamma variant contains 12 mutations and Delta contains 13. These variants are difficult for the immune system to attack and weaken the body’s response to the virus.

  In comparison to the earlier variants, Omicron contains 53 mutations, 30 of which are on the spike protein. Of these 30, 13 are rare mutations distributed across three domains.

  In comparison to the Alpha, Beta, Delta and Gamma variants, Omicron is able to more easily fuse with target cells and evade attacks from antibodies.

  Other Omicron mutations, D614G and N501Y, increase the infection rate, and mutations E474K and K417N allow the virus to avoid antibody attacks.

  Omicron did not evolve from the previous, closely studied variants. Some scientists believe that the Omicron variant might have been circulating undetected — and therefore unsequenced — within communities for some time.

  During this period, the variant could have reproduced within the bodies of people with chronic infections or compromised immune systems, giving the variant a comparatively longer amount of time and greater number of opportunities to produce mutations.

  An alternative theory is that the strain might have grown mutations in non-human species, and then transmitted back to humans.

  Examining how the epidemic affected the US, the BA.1 strain dominated at the beginning of the year, supplanted by BA.3 in March, and by April the BA.2.12.1 strain was found in 29 percent of all infected individuals.

  Omicron subvariants BA.4 and BA.5 now account for about one-third of new infections in the US, but experts predict that these could surpass BA.2 and BA.2.12.1 within the next 30 days.

  It is known that COVID-19 vaccination can eliminate cells infected by the virus by stimulating B cells in the body to manufacture antibodies and produce cellular immunity.

  This is how the vaccines provide inoculated individuals with protection from the virus and prevent reinfection.

  However, there have been multiple cases from South Africa of individuals who had two shots of the vaccine or had been previously infected by COVID-19, but nevertheless were infected by Omicron.

  Vaccine manufacturer Moderna on June 8 announced it had developed an Omicron-specific booster shot, which it says combines the original vaccine with a new version that targets Omicron.

  Moderna claims that this shot produces 1.75 times more neutralizing antibodies against the BA.1 strain than its existing COVID-19 vaccine, but its is not known how effectively it could neutralize the BA.4 and BA.5 subvariants of Omicron.

  As COVID-19 evolves and produces new mutations, the world is faced with a fresh set of challenges. Taiwan is currently battling the BA.2 subvariant.

  Although the vaccines and antiviral drugs are able to slow severe illness, it is unknown whether these pharmaceutical interventions would be effective against the next wave of the virus.

  The disease is unpredictable, and therefore it is impossible to predict how the next variant might behave.

  Health officials must decide how best to make use of existing knowledge, resources and strategies to reassure the public, while emphasizing the feasibility of coexisting with the virus.

  My suggestion is to rapidly vaccinate the population and to continue to wear masks.

  Ian Hsu is president of Ington Biotechnologies Co Ltd.

  Translated by Edward Jones
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