ST. LOUIS, MO – A new study conducted by the Washington University School of Medicine suggests that a prior COVID-19 infection – even a mild one – may provide long-lasting, possibly life-long immunity against the virus.
The results of the study are considered promising by experts, and run in contrast with previous studies that suggested that so-called “natural immunity” garnered by previous COVID infections would quickly wane over time. However, according to Dr. Ali Ellebedy – associate professor of pathology and immunology at St. Louis’ Washington University School of Medicine – the degree of protection afforded by natural immunity may last far longer than first thought.
“Last fall, there were reports that antibodies waned quickly after infection with the virus that causes COVID-19, and mainstream media interpreted that to mean that immunity was not long-lived,” Dr. Ellebedy stated in a press release. “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.”
While the Washington University researchers discovered that antibodies generated in the human body in response to COVID-19 infection did decline in number within a few months, they say that those levels were only reduced by 10 to 20 percent of their maximum levels throughout the duration of their study.
The researchers collected blood samples from 77 individuals who had contracted COVID-19 – most of whom had mild cases – and successfully recovered; additional blood samples were collected at three-month intervals – in addition to memory B cells and bone marrow from some patients – in order to monitor antibody production.
Researchers noted that at both seven and eleven months after first contracting the virus, the majority of those in the study possessed long-lived bone marrow plasma cells (BMPCs) that secreted antibodies specific for the spike protein encoded by COVID-19. In addition, these antibodies were found to be in amounts associated with the long-lasting immunity that tetanus or diphtheria vaccinations provide.
Andreas Radbruch and Hyun-Dong Chang, researchers at the German Rheumatism Research Centre Berlin, noted in response to Washington University’s study that this antibody behavior is in-line with the human body’s typical overall response to infection.
“This is consistent with the expectation that 10–20 percent of the plasma cells in an acute immune reaction become memory plasma cells, and is a clear indication of a shift from antibody production by short-lived plasma cells to antibody production by memory plasma cells,” Radbruch and Chang said in a joint statement. “This is not unexpected, given that immune memory to many viruses and vaccines is stable over decades, if not for a lifetime.”
Reuters Fact Check has disputed the results as being conclusive since the virus is “constantly changing.”