January 20th, 2021 – According to a new study conducted by Pfizer and BioNTech, the rapidly spreading UK COVID variant is unlikely to escape from the neutralizing antibodies generated by the BNT162b2 vaccine. These encouraging findings provide additional data to support Pfizer’s in vitro study results released earlier this month.
B.1.1.7 Coronavirus Variant
The new fast-spreading coronavirus variant detected in the United Kingdom last September raised concerns among health officials. Scientists too rushed to ascertain whether the recently authorized COVID-19 vaccines can protect from it.
The SARS-CoV-2 lineage B.1.1.7 (VUI-202012/01) surprised several researchers since it harbored an “unusually large number of mutations” with as many as 10 amino acid changes in the spike (S) protein, which binds to the human ACE2 receptor for viral entry. The mutations are ΔH69/V70, ΔY144, N501Y, A570D, D614G, P681H, T716I, S982A, and D1118H.
Among them, the N501Y mutation was alarming since it altered a key residue in the receptor-binding domain (RBD) of S protein. The would result in an increased affinity of S RBD towards ACE2, meaning there would be tight binding between the virus and the host cell. This mutation is also found in the variant identified in South Africa.
However, vaccine manufacturers expressed confidence that their vaccines can work against variants. Both Pfizer and BioNTech, who partnered to develop the BNT162b2 mRNA vaccine, strongly believed that this problem could be sorted, given B.1.1.7’s proteins are 99% the same as that of the original SARS-CoV-2 strain.
Encouraging Studies Supporting BNT16b2 Efficacy against Variants
On January 8th, Pfizer and BioNTech announced results from an in vitro study showing that the BNT162b2-immune sera derived from 20 vaccinated individuals neutralized SARS-CoV-2 that harbored an N501Y mutation as efficiently as the original Wuhan strain. The preliminary study results were published in the preprint server bioRXiv and are yet to be peer-reviewed.
However, it had to be investigated whether the immune sera could be effective against the full set of mutations present in the B.1.1.7 spike. To answer that, a study was performed with blood samples collected from 16 vaccinated individuals who participated in an earlier Phase 1/2 trial. Blood was drawn from the 16 individuals (eight from the 18-55 yrs age group and eight from the 56-85 yrs age group) at 21 days after they were administered with the second dose.
The immune sera isolated from the samples were exposed to engineered VSV-SARS-CoV-2-S pseudoviruses that either featured the unmutated SARS-CoV-2 spike or the B.1.1.7 spike harboring the 10 mutations. The 50% neutralization assay (pVNT50) showed no biologically significant difference in neutralization activity against the two pseudoviruses.
Keeping in mind the evolution of COVID-19 strains, the study stressed that further testing is required to monitor the efficacy of the vaccines against the continuous emergence of new variants. Nevertheless, the companies expressed that they are encouraged by these findings.
It would be interesting to see if these results could be replicated for the South African strain. However, BioNTech is confident that, even if a vaccine strain change is warranted, it is possible to make that adjustment quickly using its proprietary mRNA vaccine platform.
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