According to two new studies, immunity to coronavirus persists for at least one year, possibly lifetime, especially over time after vaccination. The findings may help calm fears that virus protection will be short-lived.
Together, studies show that most people who have recovered from Kovid-19 and who were subsequently immunized will not need a booster. Vaccinated people who were never infected will need shots, however, a minority of those who were infected but did not produce a strong immune response.
Both the reports looked at people who had been exposed to the coronavirus about a year ago. According to a study, the cells that maintain the memory of the virus persist in the bone marrow and can produce antibodies when needed. Published on monday In the journal Nature.
Another study posted online on BioRxiv, a site for biology research, found that these so-called memory B cells Continue to mature and strengthen For at least 12 months after the initial infection.
“The papers are in line with a growing body of literature that suggests that infection and vaccination for SARS-CoV-2 results in prolonged immunity,” said Scott Hensley, an immunologist at the University of Pennsylvania who was not involved in the study. Research.
Studies can allay the apprehension that immunity to the virus is transient, as is the case with coronaviruses that cause the common cold. But those viruses change significantly every few years, Dr. Hensley said. “The reason we are repeatedly infected with common coronaviruses throughout our lives may be much more with the differentiation of these viruses than with immunity,” he said.
In fact, the increased memory B cells produced and vaccinated in response to infection with SARS-CoV-2 are so potent that they also thwart variants of the virus, negating the need for boosters, an immunologist at Rockefeller University , According to Michele Nussenzweig, New York who led the study on memory maturation.
“People who were infected and vaccinated have a really terrible reaction, a fantastic set of antibodies, as they continue to develop their antibodies,” Dr. Nussenzwig said. “I hope they last a long time.”
The result may not apply only to the protection derived from vaccines, as there is a possibility of organizing immune memory differently after vaccination compared to the following natural infections.
This means that people who have not had COVID-19 and are immunized may eventually need a booster shot, Dr. Nussenzweig said. “It’s the kind of thing that we’ll be able to know very soon,” he said.
Upon encountering a virus for the first time, B cells grow rapidly and produce large amounts of antibodies. Once acute infection is resolved, a small number of cells reside in the bone marrow, continuously pumping modest levels of antibodies.
To look for memory B cells specific to the new coronavirus, researchers led by Ali Elebedy of Washington University in St. Louis analyzed the blood of 77 people over three-month intervals, starting about a month after their infection with the coronavirus. happen. Only six out of 77 were hospitalized for COVID-19; The rest had mild symptoms.
Antibody levels in these individuals dropped sharply after four months of infection and continued to decrease gradually for the following months – the results consistent with those further studies.
Some scientists have interpreted this deficiency as a sign of weakened immunity, but it is What is really expected, Other experts said. If there is a high amount of antibodies to each pathogen in the blood, it will quickly turn into a thick slime.
Instead, blood levels of antibodies drop rapidly after acute infection, while memory B cells remain inactive in the bone marrow, ready to act when needed.
Dr. Allebedy’s team obtained bone marrow samples from 19 people approximately seven months after being infected. Fifteen had detectable memory B cells, but four did not, suggesting that some people may have very few or none at all.
“It tells me that even if you have become infected, it doesn’t mean that you have a super immune response,” Dr. Allebedy said. He said the findings reinforce the idea that people who have recovered from Covid-19 should be vaccinated.
Five of Dr. Allebedy’s participants in the study initially donated bone marrow samples seven or eight months after infection and then four months later. He and his colleagues found that the number of memory B cells remained constant at that time.
The results are particularly notable because bone marrow samples are difficult to obtain, said Jennifer Gormman, an immunologist at the University of Toronto, who was not involved in the work.
a Historical study in 2007 Showed that in theory antibodies can survive for decades, perhaps even beyond the average lifespan, pointing to the long-term presence of memory B cells. But the new study offered a rare proof of their existence, Drs. Gommerman said.
Dr. Nusenzwig’s team observed how memory B cells mature over time. Researchers analyzed the blood of 63 people who had recovered from Kovid-19 nearly a year earlier. Most participants had mild symptoms, and 26 also received at least one dose of the Modern or Pfizer-BioNotech vaccine.
The team found that the so-called neutralizing antibodies, necessary to prevent re-infection with the virus, remained unchanged between six and 12 months, while the related but less important antibodies gradually disappeared.
As memory B cells continued to evolve, the antibodies they produced developed the ability to neutralize a broader set of variants. This ongoing maturation can result from a small fragment of the virus that is sequenced by the immune system – for target practice, so to speak.
One year after infection, the neutral activity in participants who were not vaccinated was low against all forms of the virus, with the greatest damage seen against the first identified variant in South Africa.
Vaccination has raised the level of antibodies significantly, Other studies confirm the results; The shots increased the body’s passive ability by almost 50 times.
Republican Senator Rand Paul of Kentucky said on Sunday that he would not get a coronavirus vaccine because he was infected in March last year and was therefore immune.
But there is no guarantee that such immunity will be potent enough to protect it for years, especially given the emergence of forms of coronavirus that can partially overcome the body’s defenses.
The results of Dr. Nussenzwig’s study suggest that people who have recovered from Kovid-19 and who have subsequently been vaccinated will continue to have extremely high levels of protection against emerging forms, even without receiving a vaccine booster.
“It looks exactly like we expected a good memory to look like a B cell response,” said Marion Pepper, an immunologist at the University of Washington in Seattle.
All experts agreed that people who have never had a Kovid-19 are likely to play immunity very differently. Fighting a live virus is different from a response to a single viral protein introduced by a vaccine. And for those who had COVID-19, the initial immune response had time to mature in six to 12 months before being challenged by the vaccine.
“Those kinetics are different from someone who was immunized and then immunized again after three weeks,” Dr. The paper said. “This is not to say that they may not have a widespread response, but it may be very different.”