Pfizer and BioNTech reported results Friday from an in vitro study indicating that the antibodies from people who have received their COVID-19 vaccine BNT162b2 are able to effectively neutralise SARS-CoV-2 with a key mutation that is also found in two highly transmissible strains. The findings were published on the preprint server bioRxiv and have not been peer reviewed.
The mRNA-based vaccine, which was found to be 95% effective in a Phase III trial after two doses given 21 days apart, is already approved in several countries including the UK, US and Europe, where it is branded as Comirnaty. However, rapidly spreading variants of SARS-CoV-2 with multiple mutations in their spike proteins have since been reported, initially in the UK and South Africa. Pfizer and BioNTech noted that while these two rapidly spreading viruses are different, they share the N501Y mutation, which is located in the receptor binding site of the spike protein and results in it binding more tightly to its receptor.
In order to determine if BNT162b2 could neutralise SARS-CoV-2 with the N501Y mutation, a virus with this substitution was generated in a laboratory. The research examined the response to the mutant viruses in blood samples taken from 20 people who had gotten the BNT162b2 vaccine as part of the Phase III trial, with results showing their sera could neutralise virus with the N501Y mutation "as well as" they could neutralise the non-mutated virus. "While the virus tested in this experiment did not include the full set of spike mutations found on the rapidly spreading strains in the UK or South Africa…[the findings are] consistent with preserved neutralisation of a panel of 15 pseudoviruses bearing spikes with other mutations found in circulating SARS-CoV-2 strains," the companies said, adding this suggests the key N501Y mutation does not create resistance to BNT162b2.
Pfizer and BioNTech said they are "encouraged by these early, in vitro study findings," but cautioned that more data are needed to monitor the vaccine's effectiveness in preventing COVID-19 caused by new variants. "If the virus mutates such that an update to the vaccine is required to continue to confer protection against COVID-19, we believe that the flexibility of BioNTech's proprietary mRNA vaccine platform is well suited to enable an adjustment to the vaccine," they added.
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