When infected with COVID-19, the body builds a protective fleet of immune cells, and in many people, protection lasts for more than six months after the infection is resolved, according to a new study.
The· Immunity In fact, the cells appear to be so stable that immunity to the virus can last for at least several years, the study authors said. “That amount [immune] Memories are likely to prevent the majority of people from being hospitalized for years, becoming a serious illness, “said Shane Crotti, a virologist at the Lahora Immunology Institute in California. Told. New York Times, First reported on this study.
However, predicting how long immunity to the coronavirus will last can be “tricky,” Nicholas Vablet, an assistant professor at Mount Sinai School of Medicine, who was not involved in the study, told Live Science. ..
“… It’s amazing to see immune cells build up in patients for more than 6 months and suddenly crash a year later,” Vabret said in an email. However, “The only way to know if SARS-CoV-2 immunity lasts for decades is to study patients over the same period of time.”
In other words, we don’t know exactly The duration of immunity without continuing research on people who have recovered from COVID-19.However, a new survey posted to the preprint database on November 16th. bioRxivProvides a powerful hint that protection will last — apparently not for everyone, as there are some cases of individuals re-infected with the coronavirus after recovery.
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The study jumps into the ranks of the human immune system and evaluates how various lines of defense change after COVID-19 infection.
These defenses include: antibody, Binds to the virus and calls immune cells to destroy the bug or neutralize itself. Memory B cells, a type of white blood cell, help “remember” the virus after the infection is cleared and quickly increase the body’s defenses when the body is re-exposed. Another type of white blood cell, memory T cells, also learns to recognize the coronavirus and dispose of infected cells. Specifically, the authors examined T cells called CD8 + and CD4 + cells.
The authors evaluated all these immune cells and antibodies in 185 individuals who recovered from COVID-19. Although a small number of participants had never developed symptoms of the disease, most participants experienced a mild infection that did not require hospitalization. In addition, 7% of the participants were hospitalized for serious illness.
The majority of participants provided one blood sample between 6 days and 8 months after the onset of the infection. 38 participants provided several blood samples during those time points, allowing the author to track the immune response over time.
Ultimately, “the dynamics of the immune response they measure look like what they expect from a functioning immune system, so we can argue that what they find isn’t that surprising,” Vabret said. Said.
The authors found that antibodies specific for spike proteins (the surface structure of the virus) were stable for several months and began to decline about 6-8 months after infection. Five months after infection, almost all participants still had antibodies. The amount of these antibodies varies widely from person to person, but can vary up to 200 times between individuals. According to Vabret, antibody numbers usually decrease after an acute infection, so a slight decrease in 6-8 months is not surprising.
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By comparison, the memory T cells and B cells that recognize the virus appear to be very stable, the authors said. “In essence … no memory B cell disruption was observed between 50 and 240 days,” said Mark Jenkins, an immunologist at the University of Minnesota School of Medicine who was not involved in the study. Said in. ..
“Some disruption of memory T cells was observed, but the decay is very slow and may flatten at some point,” Jenkins added. A study published on July 15 found that T cells against the associated coronavirus SARS-CoV were found in patients who had recovered by 17 years, so memory T cell numbers could stabilize sometime after infection. There is a reason to think that it is sex.journal Nature..
Early in the pandemic, scientists raised concerns that immunity to the virus might diminish in about a year. This tendency can be seen in the four coronaviruses that cause the common cold. Live Science previously reported.. However, studies have shown that the body’s response to common coronaviruses may differ from the response to viruses such as SAR-CoV and SARS-CoV-2 that have jumped from animals to humans.
“I’m not sure why seasonal coronaviruses don’t induce sustained defensive immunity,” says Vabret.But new research, along with others Recently evidenceJason Sister, a professor of microbiology and immunology at the University of California, San Francisco, who was not involved in the study, suggests that SARS-CoV-2 immunity may be more potent.
That said, some participants in the new study did not initiate a long-term immune response to the new virus.Their temporary reaction is the difference in the amount of virus they were initially exposed to, or Genetics It may explain the difference, Sister said. For example Human leukocyte antigen (HLA) gene It varies widely between individuals and helps alert the immune system to foreign invaders. Live Science previously reported..
These unique differences between people may help explain cases of COVID-19 reinfection, which is relatively rare but increasing in number. Science magazine reported..
Again, scientists need to continue studying recovered patients in order to really understand how long COVID-19 immunity lasts. “Sure, we need to look six months ahead,” we need to see if the numbers of T and B cells remain high.
When immunity is long-term, one big problem is its durability vaccine.. However, it is not possible to directly compare innate immunity with vaccine-generated immunity, Vabret said.
“The mechanism by which a vaccine induces immunity is not necessarily the same as that resulting from a natural infection,” Bablet said. “Therefore, vaccine immune defenses can last longer or shorter than natural infections.”
For example Pfizer And modern Vaccines use a molecular messenger called mRNA to train the body to recognize and attack the coronavirus. “We know virtually nothing about the persistence of these reactions,” Sister said, as mRNA-based vaccines have never been approved.
“Let’s [that’s] It’s a big unknown to me, among many. “
However, with some unanswered questions remaining, the main point from the new study is that “immunity memory against SARS-CoV-2 is very stable.” And — the fingers crossed — perhaps those hopeful results will be well preserved in the future.
Originally published in Live Science.