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Omicron carries scary mutations. That doesn’t mean they work well together.

“It is important to get a sense of the full virus,” said Penny Moore, a virus expert at the National Institute for Communicable Diseases in South Africa.

November 30, 2021 / 08:50 PM IST
Representative image (Source: Reuters)

Representative image (Source: Reuters)

The omicron variant of the coronavirus has alarmed many scientists because of the sheer number of genetic mutations it carries — about 50 in all, including at least 26 that are unique to it. But more does not necessarily mean worse: Mutations sometimes work together to make a virus more fearsome, but they may also cancel one another out.

“In principle, mutations can also work against each other,” said Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle. “However, in this case evolutionary selection is more likely to lead to the spread of a new variant with favorable than unfavorable combinations of mutations.”

Still, this phenomenon, called epistasis, is why scientists are reluctant to speculate on omicron’s attributes, even though individual mutations in the variant are associated with greater transmissibility or with an ability to dodge the body’s immune defenses.

“It is important to get a sense of the full virus,” said Penny Moore, a virus expert at the National Institute for Communicable Diseases in South Africa.

Moore’s team is among dozens worldwide trying to understand whether current vaccines will work against omicron. The researchers are creating artificial versions of the virus that contain all of omicron’s mutations, rather than making judgments based on a subset of mutations.

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COVID-19 Vaccine

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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It’s a lesson researchers learned last year, when the beta variant emerged in South Africa. They estimated that variant’s ability to evade immunity based on one particular mutation, E484K. But beta also had two other mutations that turned out to affect sensitivity to vaccines.

“The combination of those three mutations was more resistance than a virus that contained only E484K,” Moore said. Studying the single mutation “turned out to be misleading.”

Omicron carries a mutation called N501Y, which is thought to allow the virus to bind to human cells more tightly. This mutation was also present in the alpha variant and was linked to its contagiousness.

“Nonetheless, it ended up being delta, which doesn’t have that particular mutation, that was more even more transmissible than alpha,” Bloom said. “That’s because delta had other mutations that enhance transmissibility.”

A variant’s contagiousness depends on how well the virus binds to receptors on human cells, but also on the stability of the virus, where in the airways it replicates and how much of it is exhaled.

Omicron has a cluster of mutations that are all linked to tighter binding to human cells. “But acting together, they might have a somewhat different effect,” Bloom said. For that reason, he added, he cannot predict how the variant will act in the body.

That will require laboratory studies, which are underway across the globe.

This article originally appeared in The New York Times.

By Apoorva Mandavilli

c.2021 The New York Times Company
New York Times
first published: Nov 30, 2021 08:50 pm
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