South African variant reduces antibody levels produced by Pifzer/BioNTech’s COVID-19 vaccine

The effectiveness of Pfizer/BioNTech’s COVID-19 vaccine could be reduced by the South African (SA) variant, a new laboratory study suggests.

The study, conducted by researchers from Pfizer and the University of Texas Medical Branch (UTMB), used an engineered version of the virus which contained all the same mutations on the spike protein that have been observed in the SA variant, also known as the B.1.351 variant.

The researchers also tested two engineered viruses that only contained certain mutations observed in the SA variant.

The researchers then used these engineered viruses to test against blood samples from individuals who had received the Pfizer/BioNTech vaccine – BNT162b2.

The results, published in The New England Journal of Medicine (NEJM), discovered that neutralisation of the B.1.351-spike virus was reduced by around two-thirds in the BNT162b2-vaccinated blood samples.

This was in comparison to the level of neutralising antibodies observed against the most common version of the novel coronavirus in US trials of the vaccine.

However, the researchers noted that it is difficult to determine the effect this reduction in antibodies will have on the vaccine’s efficacy against the SA variant.

This is because there is currently no way to determine the level of antibodies required to protect against the virus.

“It is unclear what effect a reduction in neutralisation by approximately two-thirds would have on BNT162b2-elicited protection from COVID-19 caused by the B.1.351 lineage of SARS-CoV-2,” commented the study researchers.

Pei-Yong Shim, professor at UTMB and co-author of the study, told Reuters that he believes the Pfizer/BioNTech vaccine is still ‘likely’ to offer protection against the SA variant.

In clinical trials of the jab, protection against COVID-19 was observed after a single dose, with participants having a lower antibody response than the reduced levels seen in the SA variant study.

Another study of Moderna’s COVID-19 vaccine, also published in the NEJM, reported similar results against the SA variant.

The researchers tested pseudoviruses bearing the spike protein from the original COVID-19 strain, as well as other variants, including the SA strain and the B.1.1.7 strain discovered in the UK.

They observed a decrease in neutralising antibodies against the SA variant, noting that ‘protection against the B.1.351 variant conferred by the mRNA-1273 vaccine remains to be determined’.

Both Pfizer/BioNTech and Moderna have now highlighted the importance of continued investigation into vaccine efficacy against new viral variants.