After covid-19, how immune is the person to the virus? 1:20
Jen Christensen,
(CNN) - A recent group of studies, many early-stage and not yet peer-reviewed, shows that humans have a "robust" immune response to COVID-19 that can protect them from further infection, even if they have mild symptoms. It's not yet clear how long that protection lasts, but studies indicate it could last for months.
A leading immunologist says the findings provide optimism that people will not have to endure repeated coronavirus infections. It also provides evidence that a vaccine could protect people for more than a short time.
"The hopes I had seem to be realized with these early studies," said Dr. Ian Lipkin, director of the Center for Infections and Immunity at the Mailman School of Public Health at Columbia University.
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At the beginning of the pandemic, some scientists questioned how long the body would remember the infection and continue to make antibodies, the proteins the body makes to fight an infection, to protect it. Studies showed that these antibodies decrease over time and that different people make different amounts of antibodies. It is not clear what type and level of antibody response is needed to provide protection.
"This is an accumulation of more information that allows people to feel more comfortable with the idea that we are going to have immunity that will last longer," Lipkin told CNN. "We don't know for sure, but there are some things that are interesting that gave me a basis to be optimistic."
One of the studies showed that T cells appear to be activated by this new coronavirus. T cells are important immune cells that stimulate various arms of the immune system and also attack and destroy cells already infected by a virus.
Another study that looked at donor blood samples found that a large portion of the population, between 20% and 50% of people in some areas of the United States, may have T cells that recognize the new coronavirus, even if that person it has never been infected. It is still unclear why people have them. It may be what's called cross-protection from other coronaviruses that cause the common cold. What scientists don't yet know is whether this provides protection against COVID-19, but it has potential.
"So this is very good news and it is optimistic," Lipkin said. "You know, it's a little blue sky we've been looking for."
Jennifer Gommerman, who worked on one of the first studies, found that the antibody response to this new coronavirus is "actually quite long-lasting."
"The immune response is doing exactly what we would expect," Gommerman, an immunologist at the University of Toronto, told CNN. "At least about four months, which is how far most of us can measure at this point in the pandemic," he added.
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Gommerman said there is some decrease in the level of antibodies, as would be expected in a normal immune response, but it does not subside.
Gommerman said that another study stemming from the work of immunologist Marion Pepper at the University of Washington finds that the immune response is not good for just one particular purpose. Instead, it is like a "Swiss army knife that has many different tools" to fight the new coronavirus.
Pepper's study shows that some of the T cells form memory T cells that can remain and help provide protection in the event that a person contracts the new coronavirus again. From studies looking at SARS, another coronavirus, research shows that the response of memory T cells is long-lasting.
Gommerman said that since scientists have not seen a record of reinfection, even with the pandemic so widespread, that strongly suggests that the body's immune system is working well against this threat and that reinfection is less likely.
"So this is all good news," Gommerman said. "That means that people who are infected with this new coronavirus should have the ability to mount what is called a memory immune response to protect themselves against infection."
What is unclear is how long the human body's response to the new coronavirus can provide protection. Since it's only been seven months since the pandemic, these studies cannot determine how long protection lasts, but at least one shows that even having a mild infection provided three months of protection and suggests that protection will likely last longer.
"The difficult part about durability is that it is a time dependent measure," said David Masopust, a Howard Hughes Medical Institute scholar in the department of Microbiology and Immunology at the University of Minnesota. “We would really like to know what that will look like in five years. Unfortunately, we cannot predict that today, "added Masopust. The research results are what scientists would expect from a coronavirus, he said.
"What the research shows us is encouraging: that things look normal in the sense that you have what we call humoral immunity or antibodies," Masopust told CNN.
"And it develops B cells, which can differentiate into cells that produce antibodies, and it appears that it has T cells that seemed durable, to the extent that this study was able to look at that," he added. "The bad or sad news would be if they had gotten something different from these studies."
Masopust said that while these studies are encouraging, it is not yet clear whether the immune system's memory can actually protect people from infection. "Again, that's a real-world experiment that, unfortunately, will be done by people who come into contact with the coronavirus," Masopust said.
Gommerman said the findings on this robust immune response mean that any future vaccine should also provide protection for a useful period of time.
"This enduring immunity that we are seeing means that when we create a vaccine that is well designed and safe, a vaccine can replicate what the virus does," Gommerman said. "People need to take it when it arrives."
covid-19 Immunity