A breakthrough study by researchers at Washington University School of Medicine in St. Louis found that people recovering from mild cases of COVID-19 have immune cells in their bodies that continue to pump out antibodies against the virus long after the initial infection.
According to a news release, the researchers believe that these cells could persist for a lifetime, offering long-term protection against further infections from COVID-19.
“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 Dr. Ali Ellebedy, senior author of the study and an associate professor of pathology and immunology. “But that’s a misinterpretation of the data. It’s normal for antibodies to go down after acute infection, but they don’t go down to zero; they plateau.”
Ellebedy added that he and his colleagues found antibody-producing cells in people 11 months after infection and said, “these cells will live and produce antibodies for the rest of people’s lives.”
The experts explained that during an infection antibody-producing cells multiply and circulate in the blood causing the levels of antibodies to soar. When the infection is over, these cells mostly die off. However, a portion of these antibody-producing cells migrate into the bone marrow where they continue to release low levels of antibodies to help prevent another infection, according to the news release.
Dr. Ellebedy and his co-authors on the bone marrow study had already enlisted 77 participants for a previous research trial, most of whom had mild cases of COVID-19.
Besides giving blood samples on a regular basis, 18 of the participants gave bone marrow samples months after their infection. Those study subjects returned four months later to provide a second bone marrow sample.
The scientists also retrieved bone marrow samples from 11 people who never had COVID-19 for comparison. While the antibody levels in the blood predictably dropped off as time went on, the study authors found that most of the people who had COVID-19 still had antibody-producing cells in their bone marrow.
“These cells are not dividing,” said Ellebedy. “They are quiescent, just sitting in the bone marrow and secreting antibodies. They have been doing that ever since the infections resolved, and they will continue to do that indefinitely.”
Their study was published May 24 in the journal Nature and the authors said that further research is needed to assess the immune response for people who suffered more severe illness from COVID-19.
However, the researchers warn that people who have had COVID-19 should still get vaccinated to ensure full protection against serious illness and the emerging variants. While studies have shown that 90% of people who have had COVID-19 maintain an immune response up to eight months later, there are still 10% who do not.
The current recommendation by the Centers for Disease Control and Prevention states that people previously infected with the virus should still receive both doses of the Pfizer-BioNTech or Moderna vaccine.
Food and Drug Administration Commissioner Dr. Stephen Hahn and Dr. Peter Marks, of the FDA’s vaccine division, caution that people should adhere to the recommended two doses to achieve full protection and not make any changes to the dosing schedule.