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Study says even the most mild cases of COVID-19 can grant antibody protection for life

A new study from the Washington University School of Medicine in St. Louis claims that months after recovering from mild COVID-19 cases, people still have antibodies present protecting them against the coronavirus.

These findings were published in the journal Nature on May 24th, suggesting that these mild COVID-19 cases will leave a person with enough protection to where reinfection would be unlikely (Washington University School of Medicine in St. Louis). “Last fall, there were reports that antibodies wane quickly after infection with the virus that causes COVID-19, and mainstream media interpreted that to mean that immunity was not long-lived, said senior author Ali Ellebedy, PhD, an associate professor of pathology & immunology, of medicine and of molecular microbiology.

“But that’s a misinterpretation of the data. It’s normal for antibody levels to go down after acute infection, but they don’t go down to zero; they plateau. Here we found antibody-producing cells in people 11 months after first symptoms. These cells will live and produce antibodies for the rest of people’s lives. That’s strong evidence for long-lasting immunity.” Ellebedy realized that the key to figuring out whether a coronavirus infection leads to long-lasting antibody protection lies in bone marrow.

The study included 77 participants who were giving blood samples at three-month intervals beginning roughly a month after the initial coronavirus infection. Ellebedy and her colleagues obtained bone marrow from 18 participants seven to eight months after the initial infections. Five of them came back four months later for a second bone marrow sampling. These samples were compared to bone marrow samples from people who did not have COVID-19.

Antibody levels in the blood of COVID-19 participants dropped quickly in the first few months after infection, as expected. The levels then mostly leveled off. Additionally, 15 of the 19 bone marrow samples from infected participants contained antibody-producing cells specifically targeting the coronavirus that causes COVID-19. These cells could be found four months later in the five people who returned to give a second bone marrow sample. This was not seen in any of the 11 people who had never had COVID-19. “People with mild cases of COVID-19 clear the virus from their bodies two to three weeks after infection, so there would be no virus driving an active immune response seven or 11 months after infection,” Ellebedy said.

“These cells are not dividing. They are quiescent, just sitting in the bone marrow and secreting antibodies. They have been doing that ever since the infection resolved, and they will continue doing that indefinitely.” There is more research to be done on whether those who endured more severe infections would be protected from reinfection, as inflammation is a major variable. “We need to replicate the study in people with moderate to severe infection to understand whether they are likely to be protected from reinfection,” said first author Jackson Turner, PhD, an instructor in pathology and immunology. Ellebedy and her colleagues will also be studying whether vaccination induces long-lived antibody-producing cells.

ARTICLE: JILLIAN WEIDNER
MANAGING EDITOR: CARSON CHOATE
PHOTO CREDITS: TIMES OF INDIA

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