Why are mRNA vaccines effective against severe coronavirus infection?

A team of US researchers has explored the success of the new mRNA vaccine technology used by Pfizer and Moderna to make vaccines against Covid.

The vaccines have undoubtedly been the most effective Covid vaccines developed to date. In clinical trials, both were more than 90 percent effective in preventing symptomatic infection.

Even with the Delta and Omicron variants, the vaccines remain quite effective in preventing hospitalization and death.

In the study, researchers from the Washington University School of Medicine in St. Louis and St. Jude Children’s Research Hospital that the Pfizer vaccine vigorously and sustainably activates a kind of helper-immune cell that helps antibody-producing cells create large amounts of increasingly powerful antibodies, and also drives the development of a form of immune memory.

These cells, known as T-follicular helper cells, last for up to six months after vaccination, helping the body extract better and better antibodies. Once the helper cells fall, long-lived antibody-producing cells and memory B cells help provide protection against serious illness and death, the researchers said.

Furthermore, many of the T-follicular helper cells are activated by a portion of the virus that does not appear to detect mutations, even in the highly mutated Omicron variant.

The results, published in the journal Cell, help explain why the Pfizer vaccine elicits such high levels of neutralizing antibodies, suggesting that vaccination may help many people continue to produce potent antibodies even if the virus changes.

“The longer the T-follicular helper cells provide help, the better the antibodies, and the more likely you are to have a good memory response,” said Philip Mudd, assistant professor of emergency medicine at Washington University.

“In this study, we found that these T-follicular helper cell responses just keep going and going. And what’s more, some of them respond to a portion of the virus’ peak protein, which has very little variation in it.

“With the variants, especially Delta and now Omicron, we have seen some breakthrough infections, but the vaccines have held up very nicely in terms of preventing serious illness and death. I think this strong T-follicle helper response is part of the reason why The mRNA vaccines continue to be so protective, “Mudd said.

In the study, the team aimed to understand the role of T-follicular helper cells in producing such a strong germinal center response.

The researchers recruited 15 volunteers, each receiving two doses of the Pfizer vaccine three weeks apart. The volunteers underwent a procedure to extract germinal centers from their lymph nodes 21 days after the first dose, just before the second dose; then on days 28, 35, 60, 110 and 200 after the initial dose.

None of the volunteers had been infected with SARS-CoV-2 at the start of the study. The researchers obtained T-follicular helper cells from the lymph nodes and analyzed them.

Researchers are now studying what happens after a booster dose and whether changes in T-follicular helper cells can explain why people with compromised immune systems, such as those with HIV infection, do not get a strong antibody response.


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(Only the headline and image of this report may have been reworked by Business Standard employees; the rest of the content is automatically generated from a syndicated feed.)

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