Research conducted by scientists at the University of Texas Medical Branch in Galveston, Texas, indicates that the Pfizer COVID-19 vaccine has a strong capability of countering variants not only from the U.K. and South Africa, but the variant from Brazil. The scientists had previously asserted in February that the vaccine was successful in countering the variants from the U.K. and South Africa.
The scientists wrote a letter to the New England Journal of Medicine in which they asserted that serum samples were taken from people either two weeks or four weeks after the second dose of the vaccine had been administered. The scientists explained:
New, highly transmissible SARS-CoV-2 variants that were first detected in the United Kingdom (B.1.1.7 lineage), South Africa (B.1.351 lineage), and Brazil (P.1 lineage) with mutations in the S gene are spreading globally. To analyze effects on neutralization elicited by BNT162b2, we engineered S mutations from each of the three new lineages into USA-WA1/2020, a relatively early isolate of the virus from January 2020. … We thereby produced three recombinant viruses representing each of these lineages and two additional ones in which we engineered subsets of mutations of the B.1.351 lineage.
Thus, the first recombinant virus had all the mutations found in the S gene in the B.1.1.7 lineage (B.1.1.7-spike), the second had all the mutations found in the S gene in the P.1 lineage (P.1-spike), the third had all the mutations found in the S gene in the B.1.351 lineage (B.1.351-spike), the fourth had an N-terminal domain deletion found in the B.1.351 lineage and the globally dominant D614G substitution (B.1.351-∆242-244+D614G), and the fifth had the three mutations from the B.1.351 lineage affecting amino acids in the receptor-binding site (K417N, E484K, and N501Y) and a D614G substitution (B.1.351-RBD+D614G).
“While the research needs to be validated with real-world data, it offers another reason for optimism that the Covid vaccines are generally performing well against variants of the virus,” Bloomberg reported.
The researchers’ letter explained, “All the serum samples efficiently neutralized USA-WA1/2020 and all the viruses with variant spikes. Almost all of them did so at titers higher than 1:40.”
They also highlighted the limitations of the study:
Limitations of the study include the potential for mutations to alter neutralization by affecting spike function rather than antigenicity. Therefore, each neutralization assay with a different target virus is unique, and comparisons between neutralization titers from different assays should be interpreted with caution. … Ultimately, conclusions about vaccine-mediated protection that are extrapolated from neutralization or T-cell data must be validated by real-world evidence collected in regions where the SARS-CoV-2 variants are circulating.
In early February, the Texas scientists released results of testing the Pfizer vaccine on variants from the U.K. and South Africa. They explained, “Using an infectious complementary DNA (cDNA) clone of SARS-CoV-2 we engineered three spike mutant viruses on the genetic background of clinical strain USA-WA1/2020. Mutant N501Y virus contains the N501Y mutation that is shared by both the UK and SA variants. … Mutant Δ69/70 + N501Y + D614G virus contains two additional changes present in the UK variants … Mutant E484K + N501Y + D614G virus additionally contains the E484K substitution, which is also located in the viral RBD.”
“A limitation of the current study is that the engineered viruses do not include the full set of spike mutations found in the UK or SA variants,” the researchers noted. “Nevertheless, preserved neutralization of N501Y, Δ69/70 + N501Y + D614G and E484K + N501Y + D614G viruses by BNT162b2 vaccine-elicited human sera is consistent with preserved neutralization of a panel of 15 pseudoviruses bearing spikes with other single mutations found in circulating SARS-CoV-2 strains.”