Many signs indicate that, having been ill with coronavirus, a person acquires immunity. But doctors are not yet entirely sure of this. In addition, immunity against some viruses lasts only for a short time, and the viruses themselves are capable of mutating. Is there any hope that we can forget about covid-19?
Considering what we know about other viruses, we should develop immunity against the new SARS-CoV-2 coronavirus, experts say.
“Yes, so far we can only say that we are counting on it,” says Anne Spurkland, immunologist and professor of anatomy at the University of Oslo. - We do not have enough information yet to say something more specific. But I see that there are doubts about this”.
A study in Shanghai, which VG wrote about, for example, showed that a third of all tested had low levels of antibodies after an illness. In some cases, it was not possible to detect antibodies in the blood at all.
Also earlier in April, the South Korean health department announced a positive test for coronavirus in 163 people who had previously had covid-19 and were declared recovered.
Follow the same safety rules
Since there is still some uncertainty, the health department wants those who have already been ill with covid-19 and recovered to follow all the recommendations to prevent the spread of infection.
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“A number of studies show that many people do not have antibodies in their blood after an illness. Therefore, so far there is no way to issue evidence that they have already been ill and are now immune to covid-19."
This is what Svein Høegh Henrichsen, physician and infection protection specialist, says on behalf of the Directorate of Health.
“We must take into account the possibility that a person is able to get sick several times, while continuing to transmit the virus to others. Therefore, even if a person has recovered from covid-19, he should follow the same safety rules as everyone else."
This means staying two meters away from other people and not meeting in groups of more than five people. This does not apply to those with whom you live in the same house.
May last a lifetime or only for a short time
So can we count on immunity after having been ill with covid-19? We discussed this issue with four experts.
Tone Fredsvik Gregers, an immunologist and professor at the University of Oslo, says that in general, immunity can last a lifetime or only a short period. Depends on which microorganism you were infected with.
If you have had measles or rubella, then you will have immunity for life. But immunity to whooping cough does not last long.
“There are two ways to know if you have or have had a coronavirus,” says Gregers, who, among other things, wrote a book titled Alt du må vite om vaksiner (Alt du må vite om vaksiner).
To find out if you are infected now, you need to look in your blood for the genetic material of the virus. An antibody test can be done to determine if you have been ill before. They signal that the immune system has reacted to the infection.
Prevents the virus from entering the cell
There are thorns on the surface of the coronavirus molecule, which it uses to enter cells. It binds to a receptor called ACE2.
The virus needs to enter the cell in order to begin the reproduction process, explains Tor Brynjar Stuge, researcher and professor of immunology at the Norwegian Arctic University.
“The antibodies cover the spines of the virus, which, because of this, cannot physically dock with molecules on the cell surface,” he explains.
The immune system tries to make antibodies while fighting the coronavirus infection.
“Different antibodies are produced that work not only against the spikes of the virus. But it is the ones that prevent him from entering the cage that really protect us,”says Stuge.
The first antibodies disappear after a couple of weeks
You can get the flu over and over again because the flu virus changes very quickly. And in this case, the antibodies harvested by the body no longer work.
In addition, you can get the virus again if your immune system has forgotten it.
“By themselves, antibodies are just proteins that circulate in the circulatory system. They can degrade in a few weeks,”says Tune Fredswick Gregers.
Therefore, it is necessary for the so-called memory cells to form. It is thanks to them that antibodies can continue to be produced throughout life, providing long-term protection.
“Memory cells can last for a short or long time,” says Gregers.
It depends on this how long your immunity will be. If you are threatened again, it will stimulate the memory cells and new antibodies will begin to be produced.
“But if you do not come into contact with the virus for a long time, memory cells gradually become smaller, as well as cells responsible for the production of certain antibodies. In any case, the amount of antibodies in the blood is constantly decreasing."
Presumably, there are memory cells after covid-19
If, for some reason, memory cells have not formed, immunity will only last a couple of weeks, Gregers sums up.
"In this case, it will rely only on those antibodies that were developed during the first immune response."
Could this be the case with the coronavirus? Gregers thinks this is unlikely. She does not know a single virus, upon reaction to which memory cells would not be produced.
"I'm sure these cells are being produced, but it's still unclear how long they live."
Other coronaviruses may provide a clue
In addition to SARS, MERS, and SARS-Cov-2, there are at least four more coronaviruses. They are responsible for 20% of all colds and rarely result in any serious illness.
Not much research has focused on immunity against the common cold coronaviruses, says Anne-Marte Bakken Kran, chief physician at the Institute of Public Health.
“Judging by the way they behave in different regions, it seems that the population has a kind of collective immunity to them, otherwise we would have encountered them much more often. But this immunity is probably rather short-lived, although antibodies to them have been found,”says Kran.
A person does not appear to develop lifelong immunity to these harmless viruses, although they do not change as much as the flu virus.
In a 1990 study, fifteen volunteers were infected with the coronavirus. A year later, fourteen of them were injected with the same virus again. Some fell ill again, but with very mild symptoms.
“After getting sick with the respiratory virus, you remain relatively protected only for a while. I'm talking about a year or two. This is what we know about seasonal coronaviruses,”said Ann Falsey, professor of infectious diseases at the University of Rochester Medical Center, on the American radio station KCUR-FM.
Antibodies also to SARS and MERS
A study published on the Medrxiv.org website, which studied doctors who have had SARS, shows that although the level of antibodies in their blood decreased in the first couple of years, they could still be detected even after 12 years.
In another study, published in Emerging Infectious Diseases, antibodies in the blood of people with Middle East respiratory syndrome were detected three years after recovery. However, scientists do not know if there are enough of them to prevent re-infection.
“I want to believe and hope that immunity to SARS-CoV-2 will last for at least a couple of years if the person is not exposed to too much viral load,” says Gregers. - In the coming years, more and more people will acquire immunity. If the virus does not disappear completely, and we are exposed to it from time to time, immunity, of course, will strengthen and last longer, since memory cells will constantly be activated. Thus, to some extent, we will achieve collective immunity among the population, but this will take time."
Not just antibodies
Spurkland read a study from Shanghai that said a third of the subjects had very little or no antibodies against coronavirus in their blood. Does this mean that they have no immunity to it? And is it sure that if there are antibodies, then the person is immune to the virus?
“In general, antibodies are mentioned to say something about immunity,” says the professor.
If you have antibodies to the virus, then you are immune to it.
“This is the optimal goal that we can set, wanting to test a large number of people and without spending too much effort on it. Then we must assume that with antibodies, the body is protected from re-infection. But it cannot be ruled out that the symptoms will appear again. However, if this virus behaves in the same way as others, at least the second time you will not get a serious illness."
Antibodies are not the only thing that matters.
"There may be white blood cells in the blood, leukocytes, which have played a big role in recovery and which we cannot measure."
Anne-Martha Bakken Crane from the Institute of Public Health says the same.
“There is no certainty that only the antibodies that we are measuring now provide protection. Besides them, there is also cellular immunity, which is not taken into account in such analyzes."
“The only thing that helps to determine with certainty whether a person is immune or not is whether he gets sick again,” says Spurkland. "I think you need to stay calm and wait." She recalls that the disease has been known for only four months.
It looks like the virus stays in the body longer than usual
There are cases when the test for coronavirus turned out to be positive after a person was declared healthy. But that doesn't mean he really got infected a second time, Spurkland explains.
“It seems to me that the fact is that this disease takes many weeks longer than we expect,” she says.
While you usually recover from the flu in a week or two, covid-19 appears to be a much longer illness. You may feel better and then the condition will worsen again.
“Usually, if a person becomes infected with a virus, then in the first week, the immune system only adapts. I have to be ill with a temperature and the like. In the second week, antibodies and leukocytes come into play, and you gradually get better. But if someone you know gets sick with coronavirus, it will most likely take a long time until he recovers."
Spurkland believes that if someone, after recovery, had a positive test for coronavirus after a previous negative one, then this is more a problem of the testing system, and not immunity, as it might seem.
"This probably means that it really takes a lot of time to get rid of the virus and gain immunity, and that's another story."
Anne-Marthe Bakken Kran also believes that this is more likely from an immunological point of view.
"It happens often. We know that some people have small amounts of the virus in their blood, but they are not necessarily contagious. This indicator may be just on the border of the minimum value that the analysis shows. And this can go on for quite a long time."
Less likely to acquire immunity if the disease is mild?
Many people ask the question: "What if the disease is mild and almost without symptoms, and you can't earn immunity?" Epidemiologist and infectious disease specialist Marc Lipsitch writes about this, for example, in The New York Times.
Tune Fredswick Gregers also believes that this is very important to study in the future.
Anne Spurkland says that in general, there should be no connection between the intensity of symptoms during a viral infection and the formation of immunity.
“In theory, there is no direct connection here. You can perfectly develop enough antibodies with a vaccine. And in this case, the symptoms are very mild, if any."
“Symptoms are the result of your immune system working hard to heal you. They show how much work she has to do, but they show a good future immunity,”says Spurkland.
Will the virus remain in the body?
There are examples of viruses that we cannot completely get rid of. For example, herpes viruses remain in the carrier for life, and symptoms can occur periodically when immunity weakens.
Hepatitis B is an example of a virus that can result in various diseases, some of which are asymptomatic, while others cause severe liver inflammation. Some people become chronic carriers of it.
“In the case of this virus, the disease can proceed in completely different ways. Perhaps the same is true with the coronavirus. But in general, in my opinion, it does not seem that this is so,”says Spurkland.
Some speculate that the virus will spread in waves in the coming years, because, apparently, immunity to it lasts only for a short time.
“Now it doesn't bother me much. I think it will be a bit like the flu. We will still have some immunity by the time everything starts anew, it will not have time to disappear completely. Already, of course, not as good as at first, but still the course of the disease will not be so difficult."
When will the antibody test be available?
Many countries are now trying to organize mass antibody testing among the population. So we can learn more about how the disease actually spread, and also get more information about immunity.
Anne-Marthe Bakken Kran previously said that the Institute of Public Health ordered similar tests and is now evaluating them.
"Both the Institute of Public Health and other microbiology laboratories currently in operation are testing and verifying these antibody tests."
The problem is that the whole world wants to get it right now, she says. "Therefore, there may be difficulties with the speed and regularity of supplies."
“The most exciting initiative comes from the Oslo University Hospital. Her immunology department has developed an antibody detection system based on slightly different principles than the others. This is a very promising project."
Kran expects that antibodies will be taken in Norway in a couple of weeks.
Immunity to norovirus is short-lived
Crane also believes that, based on what scientists know about other viruses and immunology, most likely there is reason to believe that immunity does form after being infected with coronavirus.
Forskning: Are there any viruses, after infection with which there is no immunity for the near future?
Anne-Marthe Bakken Crane: Norovirus is known for its short-term immunity.
Norovirus causes intestinal flu.
If you're unlucky enough to get sick early in the Norovirus outbreak, you might even get sick again before it dies out.
However, the main reason is not even that immunity is very short, but that the virus constantly mutates a little, says Kran.
"Probably, within a couple of months after the illness, you will not have immunity even against the exact same virus that you have had."
Unlike the influenza virus, the coronavirus “corrects” some errors when copying, which means that it does not change so quickly, although some mutations still occur. So far, the virus looks pretty stable, according to an article on the American NPR website.
Can a person get sick with a virus and not develop immunity at all?
So can a person get sick and recover without developing any immunity at all?
“No, it was very unusual,” replies Anne Spurkland.
The same is said by the researcher and professor of immunology Thor Brunyar Stuge.
“It sounds very strange. You just need a good immune response to recover from a viral infection."
He has not heard of a single virus that the human immune system cannot fight back at all. But there are examples of such bacterial infections.
“If a person has had tetanus, then, as a rule, there are no protective antibodies in his blood. Toxins are released so little that the immune system does not give a confident response."
But he doesn't think something like this could be the case for the coronavirus.
"In my opinion, if the immune response is bad, it most likely means that the person has not got rid of the virus."
Tune Fredswick Gregers sums it up by stating that she is “almost certain or even completely certain” that immunity to the coronavirus is developing.
"If you have been ill with covid-19, you obviously have immunity to it, although it is not yet clear for how long."
Elise Kjørstad