Two new studies show that immunity to coronavirus will last for at least a year, or even a lifetime, and will improve over time, especially after vaccination. These findings may help dispel fears that the protective effects of this virus will last for a short period of time. Research shows that most people who recover from covid-19 and are subsequently immunized do not need to be protected.
People who have never been infected with the vaccine most likely need additional injections, and a small number of people who have been infected but have not developed a strong immune response also need injections, wrote New York Times.
Both studies analyzed people who had been exposed to the coronavirus about a year ago. According to a study published in the journal Nature on Monday, cells that retain viral memory survive in the bone marrow and can release antibodies when needed. Another study published on the biological research website BioRxiv found that these so-called memory B cells mature and strengthen for at least 12 months after the initial infection.
Scott Hensley, an immunologist at the University of Pennsylvania, said: “These papers are consistent with a growing body of literature, demonstrating that the immunity induced by infection and SARS-CoV-2 vaccine is durable.”
Research has quelled people’s concerns about the transient nature of virus immunity, just like coronaviruses that cause colds, but these viruses change significantly every few years, the doctor said. Hensley added: “The reason why we are often infected with common coronaviruses in our lives may be more related to the mutation of these viruses than to immunity.”
Michel Nussenzweig, an immunologist at Rockefeller University in New York, said that the memory B cells produced in response to SARS-CoV-2 infection and amplified by vaccination are so powerful that they can even prevent the virus strain, which means that there is no need to revaccinate . Led a study on memory maturity.
“People who were infected and vaccinated did have a good response, producing a lot of antibodies because they kept producing antibodies. I expect this to take a long time,” Dr. Nusenzweig told the New York Times.
The results may not be related to the protection from vaccines alone, because immune memory after immunization may have a different organization than immune memory after natural infection. This means that people who have not been infected with covid-19 and have been vaccinated may still need an additional injection. Nussenzweig: “We will know soon.”
After the first exposure to the virus, B cells multiply rapidly and produce large amounts of antibodies. Once the acute infection subsides, a small number of cells will settle in the bone marrow and continue to release an appropriate amount of antibodies. In order to observe the new coronavirus-specific memory B cells, researchers led by Ali Ellebedy of Washington University in St. Louis conducted a study. Louis began to analyze the blood of 77 people every three months starting about a month after contracting the coronavirus. Only 6 of 77 people were hospitalized due to covid-19, and the others had mild symptoms.
The antibody levels of these individuals declined rapidly four months after infection, and continued to decline slowly for several months thereafter, which is consistent with the results of other studies. Some scientists interpret this decrease as a sign of a decline in immunity, while others say that this is the expected result. If the blood contains a large number of antibodies for each pathogen that the human body encounters, it will quickly become a thick sludge. Instead, the level of antibodies in the blood drops sharply after an acute infection, while the B memory cells in the bone marrow are still dormant, ready to take action when needed.
Dr. Ellebedy and colleagues collected bone marrow samples from 10 people about seven months after the coronavirus infection. Fifteen of them have memory B cells, but 4 do not, which indicates that some people have few or no cells.
Dr. Ellebedy told the New York Times: “It tells us that despite being infected, we may not have the best immune response.” This finding suggests that people who have recovered from covid-19 should be vaccinated. Five of Dr. Ellebedy’s study participants donated bone marrow samples again seven or eight months after the initial infection and four months later. During this period, the number of memory B cells remained stable.
The University of Toronto immunologist Jennifer Gommerman (Jennifer Gommerman) said the results are particularly noteworthy because it is difficult to obtain bone marrow samples. An important study in 2007 showed that antibodies can theoretically survive for decades, and may even be much higher than the average life span, which indicates the long-term existence of memory B cells. But this new study provides rare evidence of their existence. Gommerman.
Dr. Nussenzweig and colleagues studied how memory B cells mature over time. Researchers analyzed the blood of 63 people who recovered from covid-19 about a year ago. The vast majority of participants had mild symptoms, and 26 others also received at least one dose of Moderna or Pfizer-BioNTech. The so-called neutralizing antibodies needed to prevent viral reinfection remain unchanged for 6 to 12 months, while related but minor antibodies gradually disappear.
As memory B cells continue to develop, the antibodies they produce have the ability to neutralize more strains. This continued maturity may be due to a small part of the virus being isolated or targeted by the immune system. One year after infection, the neutralizing activity of unvaccinated participants was lower than that of all forms of the virus, and the loss was the largest compared to the first discovered variant in South Africa. Vaccination significantly increased antibody levels, confirming the results of other studies. The vaccine also increased the neutralization ability of the human body by about 50 times.