Neutralizing Antibodies From COVID-19 Vaccination Effective Against Delta Variant


The investigators analyzed a panel of antibodies generated in response to the Pfizer COVID-19 vaccine and found that delta was unable to evade all but 1 of the antibodies tested.

The delta variant of SARS-CoV-2 is largely incapable of evading the antibodies generated by vaccination, according to a study published in Immunity. The investigators analyzed a panel of antibodies generated in response to the Pfizer COVID-19 vaccine and found that delta was unable to evade all but 1 of the antibodies tested.

“The fact that delta has outcompeted other variants does not mean that it’s more resistant to our antibodies compared to other variants,” said Jacco Boon, PhD, in a press release. “The ability of a variant to spread is the sum of many factors. Resistance to antibodies is just one factor. Another one is how well the variant replicates. A variant that replicates better is likely to spread faster, independent of its ability to evade our immune response. So delta is surging, yes, but there’s no evidence that it is better at overcoming vaccine-induced immunity compared to other variants.”

Previous studies have shown that both natural infection and vaccination result in lasting antibody production; however, the length of antibody response is only a single factor among many, according to the authors of the current study. An ideal antibody response includes a diverse set of antibodies with the flexibility to recognize many slightly different variants of the virus.

The investigators cultivated antibodies from cells extracted from 3 patients who had received the Pfizer vaccine. A total of 13 types of antibodies that target the original strain of SARS-CoV-2 were produced. Of these 13 antibodies, 12 were capable of recognizing the alpha and delta variants, 8 recognized all 4 variants, and 1 failed to recognize any of the 4 variants.

The usefulness of an antibody is assessed by its ability to block a virus from infecting and killing cells in a dish. Antibodies that are capable of preventing infection, called neutralizing antibodies, are considered more powerful than those that recognize the virus but are unable to prevent infection, though both types contribute to defending the body.

According to the investigators, 5 of the 13 antibodies neutralized the original strain. When testing the neutralizing antibodies against the variant viruses, all 5 antibodies neutralized the delta variant, 3 neutralized alpha and delta, and 1 neutralized all 4 variants. The antibody capable of neutralizing all 4 variants, 2C08, was separately tested against 3 additional variants and was effective against each.

“This antibody is not unique to the person we got it from,” said Ali Ellebedy, PhD, in the release. “Multiple antibodies targeting this area have been described in the literature; at least one is under development as a COVID-19 therapy. Similar antibodies have been generated by people infected in Italy and people infected in China and people vaccinated in New York. So it’s not limited to people of certain backgrounds or ethnicities; it’s not generated only by vaccination or by infection. A lot of people make this antibody, which is great because it is very potent and neutralizes every variant we tested.”


Antibodies elicited by COVID-19 vaccination effective against delta variant [news release]. EurekAlert; August 17, 2021. Accessed August 18, 2021.

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