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COVID-19 vaccines effective against most SARS-CoV-2 variants: Study

The findings, published in the journal Nature on Tuesday, also show that those infected with the virus prior to vaccination exhibit a more robust immune response to all variants than those who were uninfected and fully vaccinated.

October 12, 2021 / 05:26 PM IST
Source: AP

Source: AP

COVID-19 vaccines by Moderna and Pfizer provide protection against multiple variants of the SARS-CoV-2 virus, including the highly infectious Delta variant, according to a study.

The findings, published in the journal Nature on Tuesday, also show that those infected with the virus prior to vaccination exhibit a more robust immune response to all variants than those who were uninfected and fully vaccinated.

The results come as an increase in so-called "breakthrough" infections caused by the Delta variant among vaccinated individuals continues to raise questions about whether the vaccines offer broad protection against newly arising variants.

"Vaccines induce high levels of antibodies against Delta and most variants. And two shots are better than one,” said Akiko Iwasaki, a professor at the Yale University in the US.

The results suggest that booster shots can be effective in warding off SARS-CoV-2, the researchers said.


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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The team collected blood samples from 40 healthcare workers in the US between November, 2020 and January, 2021 before they had received vaccinations.

In the following weeks, they periodically took additional samples after the volunteers received their first and second doses of the Moderna or Pfizer-BioNTech mRNA vaccines.

The researchers then exposed the volunteers’ blood samples to 16 different SARS-COV-2 variants, including the Delta variant, and then measured antibody and T cell response to each of the variants.

The researchers found evidence of enhanced immune system response in all blood samples, although the strength of response varied by variant and by individual.

The immune response to the Delta variant in the blood of all volunteers was generally robust — and even stronger in samples collected after the individuals’ second shots, they said.

The breakthrough cases attributed to the Delta variant are unlikely to arise from a failure of vaccines, Iwasaki said.

They likely stem from the extremely infectious nature of the Delta variant, which can overcome the immune defence, she said.

Other studies have also shown that vaccinated individuals tend to have less severe infections.

The researchers also divided healthcare volunteers into two groups: Those who had been infected by COVID-19 prior to vaccination and those who had not.

The immune response of those infected prior to vaccination was more robust than for those who never been infected.

"Recovering from an initial infection is like getting a first vaccine shot,” Iwasaki added.

Follow our full coverage of the coronavirus pandemic here.

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