Study Explains Why Vaccinated People at Low Risk Amidst COVID Delta Variant Surge

A recent study done by researchers at Washington University School of Medicine in St. Louis explains that the COVID-19 Delta Variant is not particularly succcesful at evading the antibodies generated by vaccination. The Delta variant has caused a surge in infections this summer with thousands of cases and deaths.

The research findings published in the Journal Immunity on Aug. 16 brings light to why vaccinated people dodged the Delta variant surge. Researchers examined a panel of antibodies produced by people who were vaccinated with Pfizer vaccine and results show that the deadly variant was not able to evade all except one of the antibodies tested. Other variants like the Beta variant avoided recognition and neutralization by several antibodies.

In other studies done, co-senior author Ali Ellebedy, PhD, associate professor of pathology & immunology, of medicine and of molecular microbiology, states that natural infection and vaccination stimulate lasting antibody production – but length of the antibody response is just a factor in protection. The breadth of the antibodies matters as well.

The perfect antibody response comes with a diverse set of antibodies with the flexibility to identify other variants of the virus. Breadth shows strength. Even if some of the antibodies lose the capability to identify a new variant, other antibodies should remain capable of counteracting it.


“The fact that delta has outcompeted other variants does not mean that it’s more resistant to our antibodies compared to other variants,” said co-senior author Jacco Boon, PhD, an associate professor of medicine, of molecular microbiology and of pathology & immunology. “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.”

To be able to study the breadth of the antibody response to SARS – Cov – 2 or the virus that causes COVID-19, researchers of the study removed antibody-producing cells from three people who were vaccinated with the Pfizer vaccine. They studied and grew the removed cells in a laboratory and found in them a set of 13 antibodies that target the original strain.

Researchers also tested the antibodies in other four variants: alpha, beta, gamma, and delta. Out of the 13 antibodies, 12 recognized alpha and delta, eight recognized all four variants, and only one failed to identify any of the four variants.

The study also shows that five of the 13 antibodies neutralized the original strain. All five antibodies neutralized delta, three neutralized alpha and delta, and one neutralized all four variants.

“In face of vaccination, delta is relatively a wimpy virus,” Ellebedy said. “If we had a variant that was more resistant like beta but spread as easily as delta, we’d be in more trouble.”

The antibody that neutralized all four variants and other three additional variants tested separately, was called 2C08. In experiments done in animals, 2C08 also protected hamsters from the disease caused by all variants that were tested: the original variant, delta, and a mimic of beta.

According to Ellebedy, there are people who have antibodies that are as powerful as 2C08 that protects them against the COVID19 and its other variants. Research shows that about 20% of infected or vaccinated against the virus created antibodies that can identify the same spot on the virus that is targeted by 2C08. Only 008% carry mutations that allow them to escape antibodies targeting the spot.

“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,” Ellebedy said.