Pfizer, BioNTech's COVID-19 vaccine neutralises Brazil variant in lab study

According to laboratory study findings published Monday in the NEJM, Pfizer and BioNTech's mRNA-based COVID-19 vaccine BNT162b2 was able to neutralise the P.1 variant of SARS-CoV-2 that first surfaced in Brazil. The news follows a report late last week that suggested AstraZeneca's coronavirus vaccine AZD1222 also showed early evidence of being effective against the so-called Brazil variant.

In previous studies, Pfizer and BioNTech's vaccine neutralised a more contagious variant first identified in the UK, dubbed B.1.1.7, but appeared to elicit lower protective antibodies against B.1.351, another fast-spreading strain that initially emerged in South Africa.

In the latest work, researchers produced three recombinant viruses with mutations found in the S gene of each of the three lineages, as well as two additional ones containing subsets of mutations of the B.1.351 lineage. They conducted neutralisation testing using 20 serum samples obtained from 15 participants in the pivotal Phase III trial of BNT162b2, two weeks or four weeks after administration of the second dose.

The researchers said all the serum samples "efficiently neutralised" the original SARS-CoV-2 strain as well as all the viruses with variant spikes, and that "almost all of them did so at titers higher than 1:40." They noted that compared to efficacy against the original strain, neutralisation of the B.1.1.7 and P.1 variants was "roughly equivalent," while neutralisation of the B.1.351 variant was "robust, but lower."

Researchers said the findings are also "consistent with lower neutralisation titers against the virus with the full set of B.1.351-spike mutations than against virus with either subset of mutations." They pointed out that neutralising activity against B.1.351 was "robust at a geometric mean titer that was much higher than that obtained after one dose of BNT162b2," adding that "T-cell immunity may also be involved in protection."

Late last month, Pfizer and BioNTech began evaluating whether a third booster dose of BNT162b2 could improve protection, and said they were also in talks with regulatory authorities about testing a variant-specific vaccine having a modified mRNA sequence based on the B.1.351 lineage. The companies suggested at the time that this could "provide a flexible solution for rapidly adapting the vaccine for use against the B.1.351 lineage or other new strains that may emerge as possible immune escape virus variants."

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