Scientists found immunity to coronavirus could last for years

According to two new studies, it was determined that Immunity to the coronavirus lasts for at least a year, improving over time, especially after vaccination, allowing it to spread even throughout life. The findings may help allay lingering fears that protection against the virus will be short-lived.

Both studies suggest that most people who have recovered from COVID-19 and were vaccinated later will not need boosters. However, vaccinated people who have never been infected will likely need the injections. as well as a minority who were infected but did not produce a robust immune response.

Both reports involved people who had been exposed to the coronavirus about a year earlier. Cells that keep a memory of the virus persist in the bone marrow and can produce antibodies when it is necessaryaccording to one of the studies, published Monday in the journal Nature.

The other study, published online at BioRxiv, a biology research site, found that these so-called memory B cells continue to mature and grow stronger for at least 12 months after the initial infection.

“The articles are consistent with the growing number of articles suggesting that the immunity elicited by infection and vaccination against SARS-CoV-2 appears to be long-lasting.”said Scott Hensley, an immunologist at the University of Pennsylvania who was not involved in the research.

Studies may allay fears that immunity to the virus may be transient, as is the case with coronaviruses that cause the common cold. But these viruses change dramatically every few years, Dr Hensley said. “The reason we get infected with common coronaviruses multiple times throughout life could have a lot more to do with the variation in these viruses than with immunity.”, He said.

In fact, the memory B cells produced in response to SARS-CoV-2 infection and enhanced by vaccination are so potent that they even thwart variants of the virus, thus negating the need for boosters, according to Michel Nussenzweig, immunologist. at Rockefeller University of New York, who led the study on memory maturation.

“People who have been infected and vaccinated have a really great response, a great set of antibodies, because they keep building their antibodies.”says Dr Nussenzweig. “I hope they last a long time.”

The result may not apply only to vaccine-derived protection, as immunological memory is likely to be organized differently after immunization compared to that following natural infection.

This means that people who have not had COVID-19 and who have been immunized could possibly need a booster, Dr Nussenzweig said. “That’s the kind of thing we’ll know very, very soon,” added.

When they first encounter a virus, B cells proliferate rapidly and produce antibodies in large quantities. After the acute infection resolves, a small number of cells deposit in the bone marrow, constantly pumping out modest levels of antibodies.

To examine memory B cells specific to the novel coronavirus, researchers led by Ali Ellebedy of the University of Washington in St. Louis, analyzed the blood of 77 people three months apart, starting about a month after their infection. by the virus. Coronavirus. Only six of them had been hospitalized for covid-19; the rest had mild symptoms.

Antibody levels in these individuals declined rapidly four months after infection and continued to slowly decline for months thereafter., results in line with those of other studies.

Some scientists have interpreted the decline as a sign of declining immunity, but that’s exactly what was expected, other experts said. If the blood contained large amounts of antibodies against all pathogens encountered by the body, it would quickly turn into a kind of thick sludge.

Instead, antibody blood levels drop dramatically after an acute infection, while memory B cells lie dormant in the bone marrow, ready to act when needed.

Dr. Ellebedy’s team obtained bone marrow samples from 19 people about seven months after their infection. Fifteen had detectable memory B cells, but four did not, suggesting that some people may have very few or no cells.

“He tells me that even though he’s infected, that doesn’t mean he has a superimmune response.”Dr Ellebedy said. The results reinforce the idea that people who have recovered from COVID-19 should get vaccinated, he suggested.

Five of Dr. Ellebedy’s study participants donated bone marrow samples seven to eight months after their initial infection and again four months later. He and his colleagues found that the number of memory B cells remained stable during this time.

The results are particularly noteworthy because bone marrow samples are difficult to obtain, said Jennifer Gommerman, an immunologist at the University of Toronto who was not involved in the work.

A landmark study in 2007 showed that in theory, antibodies could survive for decades, perhaps even well beyond the average lifespan, suggesting the long-term presence of memory B cells. But the new study offered rare proof of its existence, Dr Gommerman said.

Dr Nussenzweig’s team looked at 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 and 26 had also received at least one dose of Moderna or Pfizer-BioNTech vaccine.

The so-called neutralizing antibodies, needed to prevent reinfection of the virus, remained unchanged for six to 12 months, while related but less important antibodies slowly disappeared, the team found.

As memory B cells continued to evolve, the antibodies they produced developed the ability to neutralize an even larger group of variants.

One year after infection, neutralizing activity in unvaccinated participants was lower against all forms of the virus, with the greatest loss compared to the variant first identified in South Africa.

The vaccination dramatically boosted antibody levels, confirming the results of other studies.

Kentucky Republican Senator Rand Paul said on Sunday that he would not receive a coronavirus vaccine because he was infected in March of last year and therefore was immune.

But there’s no guarantee that such immunity will be strong enough to protect you for years to come, especially given the emergence of variants of the coronavirus that can partially bypass the body’s defenses.

The results of Dr. Nussenzweig’s study suggest that people who have recovered from COVID-19 and were subsequently vaccinated will continue to have extremely high levels of protection against emerging variants, even without receiving a vaccine from COVID-19. reminder in the future.

“It sounds like exactly what we would expect from a good memory B cell response,” said Marion Pepper, an immunologist at the University of Washington in Seattle who was not involved in the new research.

All experts agreed that immunity is likely to develop very differently in people who have never had COVID-19. Fighting a live virus is different from responding to a single viral protein introduced by a vaccine. And in those who had coronavirus, the initial immune response was allowed to mature between six and 12 months before being elicited by the vaccine.

“These kinetics are different from that of a person who was immunized and then vaccinated again three weeks later.”Dr Pepper said. “That’s not to say they don’t have such a broad answer, but it could be very different.”

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