Efficacy of Pfizer Vaccine Tested

The new SARS-CoV-2 variants are suspected of producing different and severe clinical features compared to the original strain. Experts now reported the efficacy of the Pfizer vaccine and REGN-COV2 antibody against SARS-CoV-2 variants.

The results were published in the journal mBio, an open-access journal of the American Society for Microbiology.

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‘Pfizer BNT162b2 neutralized the South African variant and the Brazil variant with a 3-fold decrease in titer.’

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Dr. Landau and colleagues in the NYU Department of Microbiology and NYU Langone Vaccine Center used pseudotype viruses and convalescent sera in their study.

So, what are they?

Pseudotype viruses are replication-defective viral particles formed with a structural and enzymatic core from one virus and the envelope glycoprotein of another. They are used for research purposes.

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The convalescent serum is the blood serum received from an individual who had already been recovered from an infectious disease. It contains antibodies against the pathogen that caused the infection.

The team created a panel of pseudotype viruses that combined the HIV and SARS-CoV-2 spike protein. Sera from people who had received the Pfizer SARS CoV-2 vaccine and people who had already had COVID-19 were tested against SARS-CoV-2. The mutants considered in the study were,

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• B.1.1.7 lineage variant identified in the United Kingdom,

• B.1.351 lineage variant identified in South Africa,

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• B.1.1.248 lineage variant identified in Brazil,

• COH.20G/677H lineage variant identified in Columbus, Ohio,

• 20A.EUs variant identified in Spain and later found elsewhere in Europe, and

• Mink cluster 5 spike proteins located in minks in Denmark.

In another study, the team also tested the efficacy of REGN-COV2 , a two recombinant monoclonal antibody cocktail that contains casirivamab and imdevimab against SARS-CoV-2 variants.

Study findings :

• Convalescent sera effectively neutralized the variants with only a small decrease in titer.

• Pfizer BNT162b2 neutralized the South African variant and the Brazil variant with a 3-fold decrease in titer.

• The antibody cocktail neutralized the South African and Brazilian variants with a 9 to 15-fold decrease in titer.

"Our interpretation of the results is that the vaccine antibodies are very powerful, and even if you lose 3-fold of the titer, there is still plenty of antibody there to neutralize the virus. We believe the findings demonstrate that the vaccines will remain protective against the variants that we tested," said Dr. Landau.

Source-Medindia