Pfizer/BioNTech Vaccine Demonstrates Protective Efficacy Against SARS-CoV-2 N501Y Mutant Strain

Last December, researchers in the United Kingdom discovered that a highly contagious SARS-CoV-2 variant was spreading within the country. Subsequently, a new rapidly transmissible viral variant was also identified in South Africa. These fast-spreading variants quickly garnered global attention, not only because they could make the pandemic more difficult to control, but also due to concerns that emerging genetic mutations might render currently deployed COVID-19 vaccines ineffective. Both new variants carry the N501Y mutation in the spike protein. This mutation has drawn particular attention from researchers because it is located in the receptor-binding domain (RBD) of the spike protein. The RBD is the key protein domain that binds to the ACE2 receptor on human cells, mediating SARS-CoV-2 entry into cells. The N501Y mutation enhances the binding affinity between the RBD and the ACE2 receptor. Pfizer and Moderna have sequentially initiated experiments to evaluate the protective efficacy of their respective COVID-19 vaccines against these variants.

Recently, researchers from Pfizer and the University of Texas Medical Branch published their latest study on the preprint server bioRxiv, showing that the COVID-19 vaccine BNT62b2, jointly developed by Pfizer and BioNTech, retains the same protective efficacy against viral strains carrying the N501Y genetic mutation.

Image source: Reference [1]

Researchers introduced the N501Y mutation into the SARS-CoV-2 strain (N501) used for the development of BNT162b2, generating a new viral strain (Y501). Apart from the substitution of asparagine (N) with tyrosine (Y) at position 501 of the spike protein, the new strain is identical to the original SARS-CoV-2 strain.

▲ Schematic diagram of the construction of the Y501 viral strain (Image source: Reference [1])

They then obtained serum samples from 20 volunteers who participated in the clinical trials of the BNT162b2 COVID-19 vaccine. These volunteers received two doses of BNT162b2 at an interval of three weeks, and serum was collected 2–4 weeks after administration of the second dose.

Researchers measured the neutralizing titers of 20 serum samples against two different viral variants (N501 and Y501). The experimental results showed that the neutralizing titers of the same sera against Y501 did not decrease compared to those against N501; instead, they exhibited a slight increase numerically (higher titers indicate stronger neutralizing capacity of the serum).

▲Comparison of neutralizing titers against N501 (black) and Y501 viruses (red) in 20 serum samples (Image source: Reference [1])

Researchers stated that a limitation of this study is that the constructed Y501 virus did not incorporate all the new genetic mutations present in the spike proteins of the variants identified in the United Kingdom and South Africa. Therefore, they will continue to conduct experiments to evaluate the protective efficacy of COVID-19 vaccines against other variants. Nevertheless, these experimental results are consistent with previous findings regarding 15 other SARS-CoV-2 variants, demonstrating that BNT162b2 provides comparable protective efficacy against all these variants.

Note: This article is intended to introduce medical and health research and does not constitute a recommendation for treatment plans. For guidance on treatment options, please consult a licensed healthcare provider at a reputable hospital.

References:

[1] Xie et al, (2021). Neutralization of N501Y mutant SARS-CoV-2 by BNT162b2 vaccine-elicited sera. bioRxiv, doi: https://doi.org/10.1101/2021.01.07.425740.

[2] Pfizer-BioNTech vaccine not affected by mutation seen in contagious coronavirus variant, study indicates. Retrieved January 8, 2021, from https://www.statnews.com/2021/01/08/pfizer-biontech-vaccine-mutation-contagious/

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