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If previously COVID-19 infected, single Covaxin dose draws same antibody response as two doses

The study was undertaken to examine SARS-CoV-2–specific antibody responses after day zero (baseline, before vaccination), day 28 plus/minus two days post-first dose (month 1) and day 56 plus/minus two days post-first dose (month 2) of BBV152 in a group of healthcare professionals as well as frontline workers.

August 28, 2021 / 04:31 PM IST
Vial of Covaxin (File image)

Vial of Covaxin (File image)

A single dose of Bharat Biotech's Covaxin in previously COVID-19-infected individuals elicits a similar antibody response as obtained with two doses of the vaccine in those without a previous history of the disease, according to an ICMR study.

The study was published in the Indian Journal of Medical Research on Saturday.

"If our preliminary findings are confirmed in large population studies, a single dose of BBV152 vaccine may be recommended to previously confirmed SARS-CoV-2 infected individuals so that the naive individuals could attain the larger benefit of a limited vaccine supply," it said.

India's first indigenous COVID-19 vaccine Covaxin, codenamed BBV152, was approved by the government for emergency use in January. Two doses are given with a gap of four to six weeks.

The study was undertaken to examine SARS-CoV-2–specific antibody responses after day zero (baseline, before vaccination), day 28 plus/minus two days post-first dose (month 1) and day 56 plus/minus two days post-first dose (month 2) of BBV152 in a group of healthcare professionals as well as frontline workers.

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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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The antibody response of individuals with confirmed pre-vaccination SARSCoV-2 infection was compared with those individuals without prior evidence of infection.

As a part of the study, blood samples were collected from 114 healthcare professionals and frontline workers who received Covaxin at vaccination centres in Chennai from February to May 2021.

"Overall, good vaccine-induced antibody responses were seen in prior SARS-CoV-2–infected individuals, except in two, who received a single dose of BBV152 vaccine that was similar to antibody responses seen after a two-dose vaccination course administered to infection-naive individuals," the study stated.

"Our results in a varied group of healthcare professionals and frontline workers lend support to the previous studies (albeit mainly focused on mRNA vaccines) that increased levels of SARS-CoV-2 binding and neutralizing antibodies are present after a single vaccine dose in previously infected individuals and are comparable to the levels seen after two doses in those without prior infection," it added.

The study offers evidence in support of public health-oriented and immunologically sustained vaccine strategies.

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PTI
first published: Aug 28, 2021 04:31 pm
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