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Omicron cannot escape T cells; boosters protect households from Omicron

A key part of the immune system's second-line defense - its T cells - are highly effective at recognizing and attacking the Omicron variant, thereby preventing most infections from progressing to critical illness, a new study shows.

December 30, 2021 / 11:57 AM IST
According to the Union Health Ministry, 1.11 crore people have received two doses in India so far.  (Representational image)

According to the Union Health Ministry, 1.11 crore people have received two doses in India so far. (Representational image)


The following is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the findings and that has yet to be certified by peer review.

Omicron cannot escape body's second-line defense


A key part of the immune system's second-line defense - its T cells - are highly effective at recognizing and attacking the Omicron variant, thereby preventing most infections from progressing to critical illness, a new study shows.


Omicron's mutations help it escape from antibodies, the body's first line of defense against infection. Researchers have speculated that other components of the immune response would still target Omicron, but there has been no proof until now.

In test tube experiments, researchers in South Africa exposed copies of the virus to T cells from volunteers who had received vaccines from Johnson & Johnson or Pfizer/BioNTech or who had not been vaccinated but had developed their own T cells after infection with an earlier version of the coronavirus.



"Despite Omicron's extensive mutations and reduced susceptibility to neutralizing antibodies, the majority of T cell response, induced by vaccination or natural infection, cross-recognizes the variant," the researchers reported on Tuesday on medRxiv ahead of peer review.



"Well-preserved T cell immunity to Omicron is likely to contribute to protection from severe COVID-19," which supports what South African doctors had initially suspected when most patients with Omicron infections did not become seriously ill, they said.


The "T" stands for thymus, the organ in which the cells' final stage of development occurs.

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COVID-19 Vaccine

Frequently Asked Questions

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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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Boosters reduce risk of Omicron household transmission


The odds that vaccinated people will catch the virus if a household member becomes infected are nearly three to four times higher with Omicron than with Delta, but booster doses reduce that risk, new findings suggest.


Researchers analyzed transmission data collected from nearly 12,000 infected households in Denmark, including 2,225 households with an Omicron infection. Overall, there were 6,397 secondary infections in the week after the first infection in the house. After accounting for other risk factors, the rate of person-to-person spread of the virus to fully vaccinated people was roughly 2.6 times higher in Omicron households than in Delta households, the researchers reported on Monday on medRxiv ahead of peer review. Booster-vaccinated people were nearly 3.7 times more likely to get infected in the Omicron households than in the Delta households, they found.

Looking only at Omicron households, however, booster-vaccinated people were 56% less likely to become infected compared to vaccinated people who had not received a booster. And overall, when booster-vaccinated people were the ones who first brought home the virus, they were less likely than unvaccinated and vaccinated-but-not-boosted people to pass it to others.

Reuters
first published: Dec 30, 2021 11:57 am
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