"According to two new studies, immunity to coronavirus lasts for at least a year, and possibly for life, strengthening over time, especially after vaccination. The findings could help allay persisting fears that protection against the virus will be short-lived," New York Times.
"Collectively, the studies show that most people who recovered from Covid-19 and are subsequently immunized will not need booster immunizations. However, vaccinated people who have never been infected are more likely to need additional vaccinations, as are the minority who have been infected., but they did not develop a strong immune response, "the article says.
“Both studies studied people who contracted the coronavirus about a year ago. According to one study published Monday in the journal Nature, cells that retain the memory of the virus remain in the bone marrow and can produce antibodies whenever needed. published online on BioRxiv, a biological research website, showed that these so-called memory B cells continue to mature and harden for at least 12 months after the initial infection, "the article says.
"This work is consistent with a growing body of literature suggesting that the immunity caused by infection and vaccination against SARS-CoV-2 appears to be long-term," said Scott Hensley, an immunologist at the University of Pennsylvania who was not involved in the study. Research could allay fears that immunity to the virus is transient, as is the case with the common cold-causing coronaviruses. But these viruses change significantly every few years, Dr. Hensley noted. "The reason we continually contract common coronaviruses throughout our lives may have more to do with variations in these viruses rather than immunity," he said.
"According to Michel Nussenzweig, an immunologist at Rockefeller University in New York who has led the research on the maturation of memory cells, these B cells, produced in response to infection with SARS-CoV-2 and boosted by vaccination, are so potent that they discourage even options. virus, which eliminates the need for additional vaccinations. "People who have had an infection and then vaccinated do develop a powerful response, a powerful set of antibodies, because they continue to produce antibodies," said Dr. Nussenzweig. "I expect them to last for a long time."
“(…) People who have not had Covid-19 and have been immunized may eventually need revaccination, says Dr. Nussenzweig.“This is something we will find out very, very soon,”he added.
"When they first encounter a virus, B cells multiply rapidly and produce large amounts of antibodies. Once the acute infection resolves, a small number of cells are deposited in the bone marrow, constantly producing moderate levels of antibodies," the newspaper writes.
"To study memory B cells specific to the new coronavirus, researchers led by Ali Hellebedi of the University of Washington in St. Louis analyzed the blood of 77 people at three-month intervals, starting about a month after they were infected with the coronavirus. Only 6 of 77 were hospitalized due to with Covid-19; the rest had mild symptoms.Antibody levels in these people dropped rapidly four months after infection and continued to decline slowly for several months after that - the results are in line with other studies, "the newspaper said.
"Some scientists interpreted this decline as a sign of weakening immunity, but according to other experts, this is exactly what is expected. If the blood contained large amounts of antibodies to all pathogens that the body has ever encountered, it would quickly turn thick sediment, "the article emphasizes." Instead, the level of antibodies in the blood drops sharply after an acute infection, while memory B cells are stored in the bone marrow, ready to act when needed."
"Dr. Hellebedy's team took bone marrow samples from 19 people about seven months after they were infected. 15 had detectable memory B cells and 4 did not, suggesting that some people may have very few cells or there won't be any at all. "It tells me that even if you become infected, it does not mean that you have a super immune response," says Dr. Hellebedy. According to him, the data obtained supports the idea that people who have recovered from Covid -19 must be vaccinated.
"5 participants in Dr. Hellebedy's study donated bone marrow samples 7 or 8 months after the initial infection and again after 4 months. He and his colleagues found that the number of memory B cells remained stable during this time," reports The New York Times …
(…) "Dr. Nussenzweig's team studied how memory B cells mature over time. Researchers analyzed the blood of 63 people who had recovered from Covid-19 about a year earlier. The vast majority of participants had mild symptoms, 26 of them also received at least one dose of Moderna or Pfizer-BioNTech vaccine. The team found that the so-called neutralizing antibodies needed to prevent re-infection with the virus remained unchanged for 6 to 12 months, while associated, but less important antibodies gradually disappeared, "the newspaper points out …
"As memory B cells continued to develop, the antibodies they produced developed the ability to neutralize an even broader group of variants. This continued maturation may be the result of a small piece of virus that is isolated by the immune system - for targeted practice, so to speak."
“One year after challenge, the neutralizing activity in participants who were not vaccinated was lower for all forms of the virus, with the greatest losses observed for the variant first identified in South Africa. Vaccination significantly increased antibody levels, confirming the results of other studies; vaccinations also increased the neutralizing ability of the body by about 50 times."
(…) “All experts agree that immunity is likely to work very differently in people who have never had Covid-19. Fighting a live virus is different from responding to a single viral protein given with a vaccine. in those who were infected with Covid-19, the initial immune response had time to mature within 6-12 months before being challenged with the vaccine, "the newspaper concludes. (…)