Research Press Release

Immunology: Neutralizing antibodies may be much less effective against the B.1.351 SARS-CoV-2 variant

Nature Medicine

March 26, 2021

Antibodies from people convalescing from or vaccinated against COVID-19 can neutralize the B.1.1.7 SARS-CoV-2 variant (first identified in the UK), but they may be either unable or less able to neutralize the B.1.351 variant (first identified in South Africa) when compared to the reference strain D614G. The study, based on laboratory experiments, is published in Nature Medicine. The findings indicate that vaccinated and convalescent people have some antibody protection against the B.1.1.7 variant but may still be at risk of infection with the B.1.351 strain. Nevertheless, two doses of the vaccine do boost neutralizing antibody responses to these variants.

New SARS-CoV-2 variants, including the B.1.351 and B.1.1.7 strains, have spread to different countries, which has raised concerns about their ability to evade vaccines.

Olivier Schwartz and colleagues isolated infectious B.1.1.7 and B.1.351 strains from infected people. They then tested the strains’ responses to antibodies collected from 19 vaccinated people up to 6 weeks after the first dose of the Pfizer vaccine, and from 58 unvaccinated people who had been infected with an earlier strain of the virus up to 9 months after symptoms first began.

The authors found that antibodies from convalescent patients were able to neutralize the B.1.1.7 strain, but were much less effective against the B.1.351 strain. There was a six-fold reduction in neutralizing activity, and 40% of the samples lacked any activity at all against the South African strain. Similarly, antibodies from vaccinated people were able to neutralize the B.1.1.7 strain, but had less of an effect against the B.1.351 strain. Although neutralizing activity increased after the second dose of vaccine, it remained 14 times lower against B.1.351 than against the D614G strain.

The study is of particular value because it used authentic viral strains rather than lab-engineered proxies. The authors argue that although the findings warrant further investigation, antibodies are just part of the immune system’s response to infectious viruses. Other elements of the immune system, such as the ability of T cells to attack infected cells, may be more cross-reactive against these faster-spreading variants.

The full paper is available at:


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