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Neutralizing Activity of BNT162b2-Elicited Serum

Our take —

Several variants with mutations in the S protein, the target of most vaccines including Pfizer/BioNTech, have been identified, and concerns have been raised about the efficacy of the vaccines against these variants. While the data from this study were derived from in-vitro experiments, these findings suggest that antibodies induced by the Pfizer/BioNTech vaccine robustly neutralize the three new variants from the UK, South Africa and Brazil. However, further clinical data will be needed to fully estimate the level of protection that the vaccine provides against these variants.

Study design

Other

Study population and setting

This study analyzed the ability of sera from 15 individuals who received two doses of the Pfizer/BioNTech mRNA vaccine to neutralize several of the newly identified SARS-CoV-2 variants. The authors generated mutated S-proteins from one early viral isolate to contain all the mutations in the variants of interest that were identified in the UK, South Africa and Brazil. To determine the S protein region that is more significant in lowering immune response against viral variants, 2 other viruses were made that have all the deletions seen in the South African plus two other sets of mutations in receptor binding region.

Summary of Main Findings

The study found that the sera from the fully vaccinated participants efficiently neutralized the early US isolate of the virus, as well as all tested variants. Neutralization of the South African variant was lower than other variants, but still robust relative to the US isolate and other variants, with neutralization dilution more than 1:40. Neutralization of viruses with the South African variant deletion, but with different receptor binding region mutations were higher than that of the viruses with all mutations seen in the South African variant, suggesting mutations in the receptor binding region are more significant in antibody neutralization than the deletion.

Study Strengths

The study included analysis of the mutations found in all three of the current variants of interest.

Limitations

This is an in-vitro study that focuses only on the ability of the sera from vaccinated individuals to neutralize the variants of interest. In addition to antibodies, The Pfize/BioNTech vaccine was shown to induce a cell mediated immune response as well. Given that the actual correlate of protection is unknown, further clinical studies are needed to fully determine the actual efficacy of Pfize/BioNTech vaccine against the new variants.

Value added

This study showed that Pfizer/BioNTech (BNT162b2) vaccine-induced neutralizing antibodies are effective against the three main SARS-CoV-2 variants of interests.

This review was posted on: 12 March 2021