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A new preprint study posted to bioRxiv suggests that the existing Oxford–AstraZeneca and Pfizer–BioNTech vaccines may still provide protection, albeit at a lower level, against emerging variants of SARS-CoV-2.1
Studying antibody evasion
As new variants of SARS-CoV-2 have appeared, so too has a body of research proposing that existing vaccines may not be up to the task of protecting against them. However, new preprint data from researchers at the University of Oxford suggests that vaccines may be less resistant to new strains than previously thought.
To investigate immune response to new variants, the researchers used blood samples collected from both individuals with antibodies generated from COVID-19 infection and those with antibodies generated as a result of receiving either the Oxford–AstraZeneca or Pfizer–BioNTech vaccine. They then compared the level of antibody neutralization against four strains of the virus: the “Victoria” strain and the Kent, South African and Brazilian variants.
As indicated by previous research, the authors found that the level of virus neutralization by vaccine-generated antibodies against new variants was lower than against the original strain. Compared to the Victoria strain, the variants showed the following:
- Kent – ~2.9-fold reduction for both vaccines
- Brazil – 2.9-fold reduction for both vaccines
- South Africa – 9-fold and 7.6-fold reduction for the Oxford-AstraZeneca and Pfizer-BioNTech vaccines respectively.
Both the Brazilian variant and the South African possess similar mutations in the receptor binding domain (RBD) of the virus. It was therefore assumed that the levels of virus neutralization and thus protection afforded by vaccination, would also be similar. In a press release, Professor Gavin Screaton, lead scientist on the study, said, “This study extends our understanding the role of changes in the spike protein in escape from the human immune response, measured as neutralizing antibody levels. The results suggest that P1 (Brazilian variant) might be less resistant to vaccine and convalescent immune responses than B1351 (South Africa) and similar to B117 (Kent).”
In their discussion of the results, the researchers suggested that the lower level of resistance seen in the Brazilian strain could be due to mutations outside of the RBD, pointing readers towards a study that investigated the relationship between SARS-CoV-2-neutralizing antibodies and the virus’ spike protein N-terminal domain (NTD).2
In addition to further investigation of mutations in the NTD of SARS-CoV-2, the significant reduction in virus neutralization seen in response to the South African variant led the authors to conclude that vaccine research and development should prioritize the advancement of vaccines against this variant.
Professor Andrew Pollard, chief investigator of the Oxford University vaccine trial, said in a press release: “These further efforts to investigate the relationship between changes in the virus and human immunity provide new insights that help us be prepared to respond to further challenges to our health from the pandemic virus, if we need to do so.”
1. Dejnirattisai W, Zhou D, Supasa P, et al. Antibody evasion by the Brazilian P.1 strain of SARS-CoV-2. bioRxiv. 2021. doi: 10.1101/2021.03.12.435194
2. Cerutti G, Guo Y, Zhou T, et al. Potent SARS-CoV-2 Neutralizing Antibodies Directed Against Spike N-Terminal Domain Target a Single Supersite. Cell Host & Microbe. 2021. doi: 10.1016/j.chom.2021.03.005