Recently, many scientists around the world summarized what they have learned about Omicron (an emerging variant of SARS-CoV-2) so far, as reported in Nature.

Researchers from all over the world are now studying the Omicron strain to learn more about its infectivity, pathogenicity, and immune evasion abilities. WHO announced on December 4 that cases of Omicron infection have been detected in 38 countries around the world. The recent breakthroughs in its study are attracting more and more public attention.

Omicron is quickly expanding in South Africa, with the majority of new cases occurring in Gauteng, which includes Johannesburg. On Dec. 1, there were 8,561 cases reported in South Africa, up from 3,402 on Nov. 26 and several hundred per day in mid-November.

To track the spread of an epidemic, epidemiologists utilize R (the average number of new cases of each infection transmitted). Gauteng's R was significantly below 1 in September. The South African National Institute of Communicable Diseases (NICD) determined that Gauteng's R was above 2 in late November, assumed to be early in the pandemic.

According to Tom Wenseleers, an evolutionary biologist at KU-Leuven in Belgium, Delta, the most common mutant at the time, was losing cases, implying that the Omicron strain, which had already begun to spread, was likely to spread far faster than Delta. Wenseleers estimated that Omicron can infect three to six times as many people as Delta during the same time frame, based on the increase in new infection cases and sequencing data.

Researchers will observe the spread and global spread of Omicron in South Africa to better understand its spread. This may lead researchers to overestimate Omicron's rapid growth, but if the spread pattern can be verified in other countries as well, it is very strong evidence that Omicron is highly contagious.

When the Omicron mutant emerged, both Moderna and BioNTech were less confident in their mRNA vaccines, while at the same time they emphasized that they would intensify the development of vaccines for new variants.

The Omicron's fast spread in South Africa suggests that it has the ability to circumvent immunity. About a quarter of South Africans have been fully vaccinated, and it's likely that a large proportion of the population was infected during the previous wave, but the fact that the new strain is still spreading so quickly today shows that the previously established immune barrier isn't working, according to Wenseleers.

This is primarily because Omicron has up to 32 mutant sites in the S protein. Early analyses suggest that vaccine efficacy may be diminished. In measuring the relationship between Omicron's immune escape capacity and the number of mutations, studies have shown that the mutant would diminish the effectiveness of neutralizing antibodies. A paper published in Nature in September 2021 by a team of Rockefeller University researchers who designed a highly mutated SARS-CoV-2 variant that mimics the mutation in Omicron, demonstrates that mutations in the S protein are fully resistant to neutralizing antibodies in most people who receive two doses of mRNA vaccines or recover from COVID-19.

How will vaccine development organizations respond to Omicron?

If Omicron can evade neutralizing antibodies, this does not mean that the immune response triggered by vaccine and prior infection will not provide protection against it. Other parts of the immune system, particularly T cells, may be less affected than antibody response.

The South African researchers planned to measure the activity of T cells and natural killer cells, which has important implications for prevention efforts in patients with COVID-19 severe disease.

Breakthrough infections have previously been reported for all three vaccines used in South Africa, from Johnson & Johnson, Pfizer/BioNTech, and Oxford/AstraZeneca. Although the vaccines are virtually ineffective in mild and moderate cases, yet can prevent severe disease.

The same is true for Omicron, and the clinical value of different vaccines to counter the threat of Omicron mutant should be re-evaluated.

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