Antibodies elicited by COVID-19 vaccination effective against Delta variant: study

CHICAGO - The Delta variant of COVID-19 is not particularly good at evading the antibodies generated by vaccination, according to a study of Washington University School of Medicine in St. Louis.

Previous studies had shown that both natural infection and vaccination elicit lasting antibody production. While the length of the antibody response is one aspect of protection, the breadth matters, too.

To assess the breadth of the antibody response to SARS-CoV-2, the virus that causes COVID-19, the researchers extracted antibody-producing cells from three people who had received the Pfizer vaccine, grew the cells in the laboratory and obtained from them a set of 13 antibodies that target the original strain that began circulating last year.

The researchers tested the antibodies against four variants of concern: Alpha, Beta, Gamma and Delta. Twelve of the 13 recognized Alpha and Delta, eight recognized all four variants, and one failed to recognize any of the four variants.

The researchers found that five of the 13 antibodies neutralized the original strain. When they tested the neutralizing antibodies against the new variants, all five antibodies neutralized Delta, three neutralized Alpha and Delta, and only one neutralized all four variants.

The antibody that neutralized all four variants of concern, as well as three additional variants tested separately, was called 2C08. In animal experiments, 2C08 also protected hamsters from disease caused by every variant tested: the original variant, Delta and a mimic of Beta.

Using publicly available databases, the researchers discovered that about 20 percent of people infected or vaccinated against SARS-CoV-2 create antibodies that recognize the same spot on the virus that is targeted by 2C08. Moreover, very few virus variants, only 0.008 percent, carry mutations that allow them to escape antibodies targeting that spot.

The findings were published Monday in the journal Immunity.