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Pfizer COVID-19 vaccine provides partial protection against Omicron: Study

The yet-to-be peer reviewed study, posted on the pre-print repository medRxiv on Tuesday, also found that considerable immunity is retained in people who were both vaccinated and previously infected.

December 08, 2021 / 12:39 PM IST
Source: Reuters

Source: Reuters

The Pfizer COVID-19 vaccine provides less immunity against Omicron than from other coronavirus variants, according to a lab study that suggests a booster may still provide good protection.

The yet-to-be peer reviewed study, posted on the pre-print repository medRxiv on Tuesday, also found that considerable immunity is retained in people who were both vaccinated and previously infected.

The emergence of Omicron has raised concerns that, based on the large number of mutations in the spike protein and elsewhere on the virus, this variant will have considerable escape from vaccine elicited immunity.

The SARS-CoV-2 virus uses the spike protein to enter and infect the human cells. "The clinical implications of these important laboratory data need to be determined. It is likely that lesser vaccine-induced protection against infection and disease would be the result," said Professor Willem Hanekom, executive director at Africa Health Research Institute, South Africa.

"Importantly, most vaccinologists agree that the current vaccines will still protect against severe disease and death in the face of Omicron infection. It is therefore critical that everyone should be vaccinated," Hanekom said in a statement.

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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 researchers investigated whether Omicron escapes antibody neutralisation elicited by the Pfizer mRNA vaccine and if the virus still requires binding to the ACE2 receptor on human cells to infect them.

They used a human lung cell line clone engineered to express the ACE2 receptor to both isolate the virus and test neutralisation. The research finding indicated that ACE2 is required for Omicron entry.

The researcher also tested the ability of plasma from Pfizer vaccinated study participants to neutralise Omicron versus ancestral D614G virus.

They tested 14 plasma samples from 12 participants, with six having no previous record of SARS-CoV-2 infection nor detectable antibodies indicative of previous infection.

The remaining six participants had a record of previous infection in the first SARS-CoV-2 infection wave in South Africa where infection was with ancestral D614G variant.

These samples had very strong neutralisation of D614G virus, consistent with sampling soon after vaccination, according to the study. However, neutralisation from the vaccine for Omicron saw a 41-fold decline, the researchers said.

However, neutralisation from the vaccine for Omicron saw a 41-fold decline, the researchers said. Five of the participants who were previously infected showed relatively high neutralisation titers with Omicron, they said.

"Previous infection, followed by vaccination or booster is likely to increase the neutralisation level and likely confer protection from severe disease in Omicron infection," the authors of the study said.

The researchers noted that for Beta variant immune escape from Pfizer has been reported to be substantial with about 3-fold reduction. "The results we present here with Omicron show much more extensive escape," they added.
PTI
first published: Dec 8, 2021 12:40 pm

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