COVID-19 immunity robust eight months after infection, study says
Daily News Article — Posted on January 11, 2021
The paper, published Wednesday in the journal Science, analyzed blood samples from 188 patients mostly from San Diego who had contracted the virus.
“There was a lot of concern originally that this virus might not induce much memory. Instead, the immune memory looks quite good,” co-author Shane Crotty, a researcher at the La Jolla Institute for Immunology, told MIT Technology Review.
Crotty and his team found that most patients had virus-specific antibodies in their bloodstream six months or more after infection.
But more importantly, they had robust levels of memory B cells, which create antibodies.
In some cases, they had more of these immune cells eight months after their infection than they did after only one.
If the person becomes infected again, the memory B cells could provide a blueprint on how to fight the virus even if they have low levels of antibodies.
The findings suggest that a person who has recovered may have immunity that lasts years.
Crotty said they will continue to track the participants in the study to see if they still have the same levels of B cell counts at 12 and 18 months after infection.
But despite the promising findings, Crotty reiterated that reinfection is still possible.
“Immunity varies from person to person, and uncommon individuals with weak immune memory still may be susceptible to reinfection,” he said.
Published at nypost .com. Reprinted here for educational purposes only. May not be reproduced on other websites without permission from the New York Post.
Read an excerpt of the Jan. 6 press release from the La Jolla Institute for Immunology:
New data suggest that nearly all COVID-19 survivors have the immune cells necessary to fight re-infection.
“Our data suggest that the immune response is there–and it stays,” LJI Professor Alessandro Sette, Dr. Biol. Sci., who co-led the study with LJI Professor Shane Crotty, Ph.D., and LJI Research Assistant Professor Daniela Weiskopf, Ph.D.
“We measured antibodies, memory B cells, helper T cells and killer T cells all at the same time,” says Crotty. “As far as we know, this is the largest study ever, for any acute infection, that has measured all four of those components of immune memory.”
The findings, published in the January 6, 2021, online edition of Science, could mean that COVID-19 survivors have protective immunity against serious disease from the SARS-CoV-2 virus for months, perhaps years after infection.
The new study helps clarify some concerning COVID-19 data from other labs, which showed a dramatic drop-off of COVID-fighting antibodies in the months following infection. Some feared that this decline in antibodies meant that the body wouldn’t be equipped to defend itself against reinfection.
Sette explains that a decline in antibodies is very normal. “Of course, the immune response decreases over time to a certain extent, but that’s normal. That’s what immune responses do. They have a first phase of ramping up, and after that fantastic expansion, eventually the immune response contracts somewhat and gets to a steady state,” Sette says.
The researchers found that virus-specific antibodies do persist in the bloodstream months after infection. Importantly the body also has immune cells called memory B cells at the ready. If a person encounters SARS-CoV-2 again, these memory B cells could reactivate and produce SARS-CoV-2 antibodies to fight re-infection.
The SARS-CoV-2 virus uses its “spike” protein to initiate infection of human cells, so the researchers looked for memory B cells specific for the SARS-CoV-2 spike. They found that spike-specific memory B cells actually increased in the blood six months after infection.
COVID-19 survivors also had an army of T cells ready to fight reinfection. Memory CD4+ “helper” T cells lingered, ready to trigger an immune response if they saw SARS-CoV-2 again. Many memory CB8+ “killer” T cells also remained, ready to destroy infected cells and halt a reinfection.
The different parts of the adaptive immune system work together, so seeing COVID-fighting antibodies, memory B cells, memory CD4+ T cells and memory CD8+ T cells in the blood more than eight months following infection is a good sign.
“This implies that there’s a good chance people would have protective immunity, at least against serious disease, for that period of time, and probably well beyond that,” says Crotty. …..
(Read the entire press release at PRnewswire.)
Background
CHALLENGE: Read a more detailed report: "Coronavirus immunity lasts at least 8 months after infection, and perhaps even years, new research shows" by Aylin Woodward, Business Insider, Jan. 7:
Immunity to the coronavirus involves more than just antibodies. T cells and B cells protect us long-term, too.
A new study found that these other elements of immunity persist at least eight months in a majority of COVID-19 patients. They could protect most people against coronavirus reinfection for years.
We now have the best answer yet to a crucial, lingering question about COVID-19: how long immunity lasts.
A new study suggests that recovered coronavirus patients likely have a robust immune memory that persists for at least eight months. This memory relies on more than just antibodies — it also involves white blood cells known as T cells and B cell that have impressive powers of recollection. Combined, these layers of protection enable the immune system to recognize and re-attack the coronavirus should it ever invade again, thereby preventing another infection.
To assess how long immunity to the virus lasts across these various layers of the immune system, scientists measured how many — and what types of — immune cells recovered coronavirus patients had months after they got sick. Their research, published Wednesday in the journal Science, offers hope that those who've already gotten infected likely won't be ill again for quite some time.
"Most people are making most parts of the immune response to this virus, and those parts are still around six to eight months later," Shane Crotty, a virologist at La Jolla Institute for Immunology in California and a co-author of the study, told Business Insider.
"This implies that there's a good chance people would have protective immunity, at least against serious disease, for that period of time, and probably well beyond that," Crotty said in a press release.
Some research has suggested that coronavirus antibodies — blood proteins that protect the body from subsequent infection — fade within a few months. But concerns about those findings can discount the role of killer T cells, which identify and destroy infected cells, as well as helper T cells that inform B cells about how to craft new antibodies.
"All of those elements are designed to work together: If in any given person one's not so great, the other arms of the immune system can compensate. So it makes sense to measure everything," Crotty said.
So his group measured both types of T cells, as well as B cells and antibodies, in blood samples from more than 185 people who'd recovered from COVID-19. Nearly 40 of the participants gave blood multiple times, some more than six months after their illness. This enabled the researchers to assess how patients' immune responses changed over time.
Their results showed that patients' levels of coronavirus-specific T cells declined slightly between four and six months, then held steady after that. The researchers think it's likely that T cells and antibodies stay consistent after that six-month mark, since that's typical of other viruses.
"It takes one to two weeks for antibodies and T cell responses to develop after an infection. Those then increase and peak," Alessandro Sette, an immunologist at La Jolla and Crotty's co-author, told Business Insider. "Between four and six months they go down, and then tend to plateau out around six months. What you see at six to eight months is what you get in terms of immune response, so that's when you want to look for any indication whether you have developed a memory or not."
The study results also indicated that patients' B cell levels increased between the one-month and six-month marks. That's especially good, Sette explained, since B cells are the source of future antibodies.
"Once the initial viral invasion is gone, B cells will stop fighting, stop making antibodies," he said. "But they're still there if the attack resumes: If you have an expanding army of B cells circulating in the body, that would regenerate a antibody response."
Antibodies, however, declined measurably by the six-month mark, according to the study. But Crotty said that decline is "quite reasonable for any infection" and not on its own a reason to be concerned.
Sette and Crotty could only look at recovered coronavirus patients eight months post-infection, since the pandemic began about a year ago. But they think the slow rate of decline in patients' T cell and B cell counts means those cells will last far longer than the time period analyzed in the study.
"The immune responses are following the expected playbook, and they're stable over at least eight months," Sette said, adding that "the trajectory doesn't indicate they're going to crash at eight months and one day."
White blood cells developed in response to other viruses can stick around for years. T cells specific to smallpox, for example, take about 10 years to disappear after an infection, while B cells for that virus stick around for 60 years.
T cells specific to SARS, another coronavirus that shares 80% of its genetic code with this new one, also seem to stick around long-term. A study from July looked for T cells in blood samples from 23 people who survived SARS. Sure enough, those survivors still had SARS-specific memory T cells 17 years after getting sick.
The new study found that about 90% of people develop robust immunity to the coronavirus — undergirded by antibodies, T cells, and B cells. But not everyone developed all three immune elements to the same degree, and a small subsection of participants developed only some, or none, of them.
Those patients seem to have "quite weak immune memory," Crotty said, so could be susceptible to reinfection relatively quickly.
"You really want to have the whole orchestra of the immune system coming together to defeat the virus," Sette said.
The reason for this person-to-person variation isn't clear, but the study authors found that patients who fared better during their bout of COVID-19 had multiple types immune cells working for them. Those who fared poorly had one or less.
But until scientists have more time to study the virus, Sette and Crotty said, there won't be a way to predict how long a given person's coronavirus immunity will last after they're infected. A future goal, the study authors said, is to track some COVID-19 patients' immune responses a year to 18 months after they got sick, as well as analyze people's immune responses after they've gotten vaccinated.
"There's just no way to do quick blood test to say you're going to have immune memory for 10 years," Crotty said. "So we'll just have to wait and see."