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How bad is Omicron? What scientists know so far

Since scientists from Botswana, South Africa alerted the rest of the world about a rapidly-emerging SARS-CoV-2 variant known as Omicron, it has been less than a week. Scientists from all over the globe are working together to discover the danger this variant poses to the world. It has been confirmed in at least 20 countries. Scientists may need to spend weeks trying to understand Omicron and its transmissibility, severity, the potential for reinfection, and ability to evade vaccines.

Nature summarizes what scientists have discovered so far about the Omicron variant.

How quickly is Omicron spreading around?
Researchers are most concerned by Omicron’s rapid growth in South Africa, as it suggests that the variant could cause explosive increases in COVID-19 incidences elsewhere. South Africa had 8,561 cases on 1 December. This is an increase from the 3,402 cases reported on 26 November and several hundred per hour in mid-November. Most of the growth was in Gauteng Province which is home to Johannesburg.

R is the number of new cases created by each infection. Epidemiologists use R to measure an epidemic’s growth. Late November saw South Africa’s National Institute for Communicable Diseases in Johannesburg determine that R was higher than 2 in Gauteng. This level of growth was last seen in the early days of the pandemic.

Wenseleers believes that Omicron could infect as many as three to six times the number of people as Delta over the same period, based on COVID-19 case increases and sequencing data. He adds, “That’s an enormous advantage for the virus — and not for us.”

Is Omicron able to overcome the immunity of vaccines and infection?
Its rapid rise in South Africa suggests that the variant may be able to evade immunity. Based on the increased death rates since the outbreak of the pandemic, around 25% of South Africans have been fully vaccinated.

Omicron’s popularity in southern Africa may be due to its ability to infect both those who have recovered from COVID-19 (due to Delta and other variants) as well as those who have been vaccinated. Researchers at the NICD discovered that Omicron spread has led to an increase in South African reinfections. Althaus says, “Unfortunately this is the ideal environment for immune-escape varieties to develop.”

Aris Katzourakis, a researcher at the University of Oxford in the UK, says that the spread of the variant may depend on factors like vaccination rates and past infection rates. It might be able to spread if it is injected into a population that has stopped taking other preventive measures.

What will the impact of vaccines on Omicron?
Omicron is capable of evading neutralizing antibodies. However, this does not mean that immunity triggered by vaccination or prior infection will not offer protection against the variant. Miles Davenport (an immunologist at Sydney’s University of New South Wales) says that mild levels of neutralizing antibodies could protect against severe COVID-19.

Omicron’s mutations may not affect all aspects of the immune system. T cells are one example. South African researchers plan to measure the activity of T cells and natural killer cells. This could be particularly important in protecting against severe COVID-19. Shabir Madhi is a vaccinologist at the University of the Witwatersrand.

Madhi has been involved in the South African COVID-19 vaccine trial trials. She is also involved in epidemiological studies to determine vaccine effectiveness against Omicron. Anecdotal evidence suggests that there have been breakthrough infections involving all three vaccines administered in South Africa: Johnson & Johnson (BioNTech), and Oxford-AstraZeneca. Madhi said that researchers would like to quantify Omicron’s protection, both by previous infections and vaccines.

Will current boosters improve protection against Omicron?
Omicron is a threat that has led some wealthy countries like the UK to accelerate and expand the distribution of COVID booster doses. It is not clear yet how effective these doses against Omicron will be.

Third doses supercharge neutralizing-antibody levels, and this will likely provide a bulwark against Omicron’s ability to evade these antibodies, says Bieniasz. His research on the polymutant spike revealed that those who had recovered from COVID-19 within months of receiving their jabs were able to produce antibodies that block the mutant spike. Bieniasz believes that those who have been exposed to SARS-CoV-2 spike protein over a prolonged period, whether through infection or booster doses, are more likely to be able to neutralize Omicron.

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