According to a study conducted by researchers at Washington University School of Medicine, St. Louis, months after healing from mild cases of COVID-19, people already have immune cells in their bodies pumping out antibodies against the virus that induces COVID-19. Such cells could live for a lifetime, producing antibodies in the process.
Mild Covid-19 Infections Induce Long-Lasting Immunity
According to the report that contradicts previous studies, mild cases of COVID-19 provide people with long-term antibody defense against reinfection.
According to study senior author Ali Ellebedy, who is an associate professor of pathology and immunology, medicine, and molecular microbiology at Washington University School of Medicine, St. Louis, last fall, there were claims that antibodies decreased rapidly after infection with the virus that induces COVID-19, and mass media interpreted that as immunity was not long-lasting.
However, this is a misunderstanding of the results. It’s common for antibody levels to drop after an initial illness, but they don’t drop to zero; instead, they stabilize, according to Ellebedy in a university news release. They discovered antibody-producing cells in people 11 months after the onset of symptoms. These cells will continue to exist and generate antibodies for the remainder of people’s lives. That’s compelling support for long-term immunity.
The study involved 77 people who provided blood samples every three months, beginning around a month after being infected with SARS-CoV-2, the virus that causes COVID-19. The majority had minor COVID-19 infections, and only six had been hospitalized.
Seven to eight months after their original coronavirus diagnosis, bone marrow samples were taken from 18 of the patients. Four months later, five people gave the second bone marrow sample.
In addition, the researchers examined bone marrow samples from 11 individuals who had never been exposed to COVID-19.
Antibody levels in the participants’ blood dropped rapidly in the first few months after infection, as predicted, and then largely leveled off, with some antibodies still detectable 11 months later.
7 to 8 months after infection, 15 bone marrow samples from COVID-19 participants contained antibody-producing cells that targeted SARS-CoV-2, and those cells were also present in the five individuals who offered a second bone marrow sample four months later.
According to the report, none of the 11 individuals who had never been exposed to COVID-19 had these antibody-producing cells in their bone marrow.
People with moderate COVID-19 infections clean the virus from their bodies 2 to 3 weeks after diagnosis, so there will be no virus driving an active immune response seven to eleven months later, according to Ellebedy. These cells aren’t proliferating. They are dormant, only existing in the bone marrow and secreting antibodies. They’ve been doing that since the virus cleared up, and they’ll be doing it forever.
According to the researchers, individuals who were infected with the new coronavirus but did not develop symptoms could have developed long-lasting immunity.
It’s unclear if people with extreme COVID-19 are immune to reinfection.
According to Jackson Turner, who is a teacher in pathology and immunology at Washington University in St. Louis and the study’s first reporter, it might go either direction.
Turner clarified in the report that inflammation plays a significant role in extreme COVID-19 and that too much inflammation will lead to faulty immune function. On the other hand, the reason that people get very sick is mostly that they have a lot of viruses in their bodies because having a lot of viruses around will lead to a strong immune system. As a result, it’s unclear. They need to repeat the research in people with mild to serious infections to see if they are likely to be safe from reinfection.
Ellebedy and colleagues are now investigating whether vaccination will cause long-lived antibody-producing cells as well.