expert reaction to preprint on neutralisation of SARS-CoV-2 viruses with variant spike proteins by convalescent sera and the Pfizer vaccine


A preprint, an unpublished non-peer reviewed study, looks at neutralisation of SARS-CoV-2 viruses with European, South African and United States variant spike proteins by convalescent plasma and Pfizer vaccine-elicited antibodies.


Dr Julian Tang, Honorary Associate Professor/Clinical Virologist, University of Leicester, said:

“Another lab study on the Pfizer vaccine now looking at the UK B.1.1.7 and South African B.1.351 variants, alongside other US and European variants.

The thing to remember about these studies is that:

– they are not using the live wildtype virus – just synthetic virus constructs (pseudo types) in culture for the neutralisation studies; 

– there is no whole human immune system present when these viruses are exposed to these vaccine-induced or convalescent plasma antibodies; 

– and that these lab studies cannot reflect the spectrum and severity of clinical illness experienced by a live human patient exposed/infected with these various live virus variants.

“Within the limitations outlined above, these in vitro studies do show a potentially reduced real-life vaccine efficacy (indicated by a 3-fold reduction in the in vitro neutralisation titres) against the South African B.1.351 variant – mostly conferred  by the E484K mutation (Figure 3) – compared to a mostly unaffected vaccine response to the UK B.1.1.7 variant (Figure 4) – as has been reported elsewhere.”


Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:

“This worthy study tests the effectiveness of antibodies generated by the Pfizer Covid-19 vaccine against the B.1.1.7 ‘Kent’, and B.1.351 ‘South African’ variants of the virus.  Unsurprisingly, and as with other vaccines, there was no decrease in efficacy towards the ‘Kent’ variant, but the antibodies were less effective against the ‘South African’ variant. This is unsurprising as the ‘Kent’ variant lacks a mutation found in the ‘South African’ variant which changes to the structure of the virus’ spike protein to reduce binding of antibodies that would block the virus attaching to its receptor on human cells.

“Measuring the amount of neutralising antibodies may not be a dependable proxy for protection against disease. Data recently released by the Oxford Vaccine group1 showed that protection against disease was not reliably mirrored by the neutralising activity of antibodies produced by someone’s immune system.  It would appear that having the right type of immune response, which we do not yet understand for Covid-19, is more important than simple quantity of antibodies.”




The preprint ‘Neutralization of viruses with European, South African, and United States SARS-CoV-2 variant spike proteins by convalescent sera and BNT162b2 mRNA vaccine-elicited antibodies’ by Takuya Tada et al. was uploaded to bioRxiv on Sunday 7th February. It has not yet undergone peer review.



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