COVID-19 patients with milder symptoms and swifter recoveries have prolonged immunity from reinfection, Harvard Medical School researchers found in a study published in the peer-reviewed journal Cell Nov. 3.
Led by Medical School professor and Brigham and Women’s Hospital immunologist Duane R. Wesemann, the study examined blood samples and immune cells from patients recently recovered from mild to moderate COVID-19 cases.
The study found that while the majority of participants experienced a decrease in COVID-19 antibody production in the months following their recovery from the virus, about 20 percent of the 92 individuals examined sustained antibody production at a rate equal to or greater than the rate during infection.
These patients, designated as sustainers for their ability to maintain COVID-19 antibody production for longer periods of time, were found to have recovered from the disease, on average, far more quickly than decayers, those who did not sustain antibody production.
“We were able to kind of identify a phenotype, or a kind of person that has a certain immune response, that is able to clear the virus more quickly and invest in an immune response that, for whatever reason, produces these long-lived plasma cells,” Wesemann said.
In addition to quicker recovery due to robust antibody responses, sustainers tended to have a profile of memory T cells and B cells — which help generate an accelerated response in the case of repeated infection — that are optimized evolutionarily, leading to an increased effectiveness in immune memory and protection.
“With the antibodies an interesting process takes place where they undergo this Darwinian process of evolution at a hyperspeed timescale,” Wesemann said.
He added that the study is “good news for vaccines” because it gives insight into how the human body responds to the novel coronavirus.
Still, he said, more questions need to be answered in order to truly understand how the virus behaves, such as why some people have more antibodies than others, and whether yearly vaccines will be needed to combat the virus.
“Why is this happening to these people?” Wesemman said. “Is it related to something that happens in common with other cold viruses, which we know don’t produce lasting immunity?”
Wesemman said the study could have implications beyond COVID-19, particularly due to the discovery that the memory T cells and B cells were undergoing somatic mutations at rates he had never considered. He said the high somatic mutation levels may be an indicator of how memory B cells behave.
The results of the study showing that some patients are able to clear the virus more quickly than others and have evidence of a superior immune response — including the development of longer plasma cells — could have implications for broader research on disease control, Wesemann said.
“This is a question that touches on a fundamental piece of immunology that we don’t understand — why some processes lead to longer plasma cells, and others don’t,” he said.