It has been more than a year since the new coronavirus appeared in our lives, but there are still many questions that doctors and scientists cannot answer.
One of the most important questions is how long will you be immune once you recover from the infection.
This is a question that everyone is puzzled by, from scientists to almost the rest of the world. At the same time, those who have received the first vaccination also want to know if they are immune to the virus.
Antibody tests can help solve some of these problems, but unfortunately, they do not provide absolute clarity about the level of immunity.
However, they can still help, and laboratory doctors, immunologists and virologists will explain in detail what you need to know.
There are two main types: tests that measure the presence of antibodies, and other tests that evaluate how well these antibodies perform against the virus.
For the latter, called a neutralization test, the serum is contacted with the part of the coronavirus in the laboratory to see how the antibody reacts and how the virus is rejected.
Although the test does not provide absolute certainty, it is safe to say that “a positive neutralization test almost always means you are protected,” said Thomas Lorentz from the German laboratory physician team.
Immunologist Carsten Watzl points out that the neutralization test is more precise. But research shows that there is a correlation between the number of antibodies and the number of neutralizing antibodies. “In other words, if I have a lot of antibodies in my blood, then all of these antibodies are unlikely to target the correct part of the virus,” he said.
This means that even simple antibody tests can provide a certain degree of protection, although the degree they can tell you is limited.
“No one can tell you what the level of real immunity is,” Watzl said. “You can use other viruses, but we have not yet reached the stage of coronavirus.” Therefore, even if your antibody levels are high, there is still uncertainty.
Lorentz said that while this varies by country, in most parts of Europe, the antibody test where doctors collect blood and send it to the laboratory for analysis may cost about 18 Euros ($22), while neutralization tests are Between 50 and 90 Euros (60-110 USD).
There are also some tests that are suitable for home use. You can take some blood from your fingertips and send it to the laboratory for analysis or drop it directly onto the test box—similar to the rapid antigen test for acute coronavirus infection.
However, Lorenz advises against doing antibody tests on your own. The test kit, and then you send your blood sample to it, which costs up to $70.
Three are particularly interesting. The human body’s rapid response to viruses is IgA and IgM antibodies. They form quickly, but their levels in the blood after infection also drop faster than the third group of antibodies.
These are IgG antibodies, formed by “memory cells”, some of which can stay in the body for a long time and remember that the Sars-CoV-2 virus is the enemy.
“Those who still have these memory cells can quickly produce many new antibodies when needed,” Watzl said.
The body does not produce IgG antibodies until a few days after infection. Therefore, if you test this type of antibody as usual, experts say you have to wait at least two weeks after infection.
At the same time, for example, if the test wants to determine whether IgM antibodies are present, it may be negative even only a few weeks after infection.
“During the coronavirus pandemic, testing for IgA and IgM antibodies was not successful,” Lorenz said.
This does not necessarily mean that you are not protected by a virus. Marcus Planning, a German virologist at the University Hospital of Freiburg, said: “We have seen people with mild infections and their antibody levels have dropped relatively quickly.”
This also means that their antibody test will soon become negative-but because of T cells, they can still get a certain degree of protection, which is another way our body fights disease.
They will not jump on the virus to prevent them from docking on your cells, but will destroy the cells attacked by the virus, making them an important part of your immune response.
He said this may be because after infection, you have relatively strong T cell immunity, which ensures that you get less or no disease at all, despite having fewer or no antibodies.
In theory, everyone who wants to test for T cells can perform blood tests based on their location, because various laboratory doctors provide T cell tests.
The question of rights and freedom also depends on where you are. There are several places that give anyone who has contracted COVID-19 in the past six months the same rights as a fully vaccinated person. However, a positive antibody test is not enough.
“So far, the only way to prove the time of infection is a positive PCR test,” Watzl said. This means that the test must be conducted for at least 28 days and no more than six months.
Watzl said this is especially meaningful for people who have immunodeficiencies or take immunosuppressive agents. “With them, you can see how high the antibody level is after the second vaccination.” For everyone else—whether vaccination or recovery—Watzl believes the importance is “limited.”
Lorenz said that anyone who wants to evaluate immune protection against the coronavirus should choose a neutralization test.
He said he could not think of any time a simple antibody test would make sense, unless you just want to know if you are infected with the virus.
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Post time: Jun-23-2021