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Immunity to the novel coronavirus could last for a year — and possibly longer — particularly after COVID-19 vaccination, according to The New York Times .
Two recent studies indicate that most people who contracted COVID-19, recovered and then got vaccinated later may not need a booster shot. Those who were never infected and then got vaccinated may need a booster shot later, the newspaper reported.
Both studies looked at people who were exposed to COVID-19 about a year ago. In a study published Monday in the journal Nature, scientists found that certain immune cells may survive in the bone marrow of people who were infected and later vaccinated. Those immune cells may create antibodies whenever needed.
In another study published on the bioRxiv pre-print server, researchers found that these memory B cells can grow and strengthen for at least 12 months after an initial infection.
"The papers are consistent with the growing body of literature that suggests that immunity elicited by infection and vaccination for SARS-CoV-2 appears to be long-lived," Scott Hensley, an immunologist at the University of Pennsylvania who wasn't involved with the research, told The New York Times.
"The reason we get infected with common coronaviruses repetitively throughout life might have much more to do with variation of these viruses rather than immunity," he said.
In the Nature study, researchers analyzed blood samples from 77 people at three-month intervals, starting about a month after their infection. Of those, six were hospitalized for COVID-19, and the rest had mild symptoms. The blood levels of antibodies fell sharply after infection, but the memory B cells remained in the bone marrow.
Among 19 bone marrow samples, 15 had detectable memory B cells about 7 months after infection. The other four did not, which could mean that some people who contract the virus don't generate a long-lasting response. The finding backs up the idea that people who have recovered from COVID-19 should be vaccinated.
"It tells me that even if you got infected, it doesn't mean that you have a super immune response," Ali Ellebedy, an immunologist at Washington University in St. Louis who led the study, told The New York Times.
In the bioRxiv study, researchers analyzed blood samples from 63 people who recovered from COVID-19 about a year before. Most had mild symptoms, and 26 had received at least one dose of the Pfizer or Moderna vaccine. The neutralizing antibodies, which prevent reinfection, were unchanged between about 6-12 months in those who had been vaccinated.
As the memory B cells matured and evolved, they were also able to neutralize some variants, the researchers found. Those who hadn't be vaccinated had lower neutralizing activity against all forms of the virus, particularly against the B.1.351 variant first identified in South Africa. That means people who have had COVID-19 and a vaccine may not need a booster, but those who have only contracted the virus or only been inoculated may eventually need one.
"That's the kind of thing that we will know very, very soon," Michel Nussenzweig, MD, an immunologist at Rockefeller University in New York, who led the study published on the bioRxiv server, told the newspaper.
"People who were infected and get vaccinated really have a terrific response, a terrific set of antibodies, because they continue to evolve their antibodies," he said. "I expect that they will last for a long time."
The New York Times: "Immunity to the Coronavirus May Persist for Years, Scientists Find."
Nature: "SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans."
bioRxiv: "Persistent Cellular Immunity to SARS-CoV-2 Infection."
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Cite this: COVID-19 Immunity Could Last for Years, Studies Say - Medscape - May 27, 2021.