The more people are infected with a virus, the more they have to be immune. This is how infectious medicine teaches it. At what point the immune system behaves differently from Sars-CoV-2 and how long an immunity could be active, explains ntv.de.
Drugs, vaccination or immunity – since the beginning of the corona pandemic, possible immunity has been one of the most important considerations for normalization. The problem so far is that it is still not clear to what extent people are actually protected from being infected again after they have been through an infection.
The World Health Organization (WHO) estimated in late April: “There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.” To date, this assessment has not been revised. However, there was an objection, including from the Berlin virologist Christian Drosten. He said in the NDR podcast: “I continue to fully assume that there is immunity.”
It is not easy to make a statement about this because human immune defense is a very complex system. The T cells play a special role in this. They also step in together with other parts of the immune system if the innate immune system is unable to destroy pathogens. However, you have to get to know the enemy first. This takes a while, but then the defense works much better because the immune response is tailored, so to speak. The information is also saved and can be called up the next time you contact the pathogen.
Antibodies don’t say that much
Two studies were reported in the science magazine “Science”, in which T cells were found in the blood of recovered patients, which were formed immediately for the Sars-Cov-2. The studies come from immunologists at the La Jolla Institute for Immunology in the USA and from immunologists at the Charité in Berlin.
In both studies, there were also some subjects who were never infected with Sars-CoV-2 and still have this cellular immune system. The researchers assume that these people were previously infected with other corona viruses. Researchers call this effect “cross-reactivity”. According to the researchers, it could be a reason why a large part of the population is not seriously ill. So far, however, this has not been investigated in studies.
It is still unclear whether people who have antibodies are actually safe from being infected again and, above all, for how long. Antibody tests that have been developed so far only provide information on whether there has been a Sars Cov-2 infection in the past. However, worldwide experience shows that 10 to 20 percent of those infected have little or no detectable antibodies in their blood. This could be due to the inaccuracy of the tests, the special properties of the corona virus or the individual defense of these people.
There are certain empirical values regarding the duration of immunity. In the 2002/03 Sars epidemic, which was also caused by a coronavirus, immunity was up to two years. For other corona viruses, it is only about three months. Imperial College scientists in London have made model calculations that indicate immunity for at least another season. In comparison: After a measles infection you are immune for life. Charité immunologist Drosten believes that the amount of antibodies in Sars-Cov-2 will decrease over time. But he also points out that antibodies alone do not bring about immunity. They are only “an indicator of an infection that has survived”.
Many uncertainty factors
Scientists are currently assuming that there is no one value for everyone. The reason for this is that each person’s immune system is configured differently. The genetic heritage, diseases that have already been through and lifestyle play a role.
Another factor of uncertainty are possible mutations in the virus. Sars-Cov-2 could change so much that the immune system no longer recognizes it as a known intruder. In addition, the mutation pressure on the virus could increase as more and more people become immune. So far, however, this has not been the case. Virus genomes have been studied in different countries, and the temporary assumption that there are now two strains has been refuted. The researchers are currently assuming that it is still the parent virus and will not become any more dangerous.
First of all, this increases the number of people who go through an individual immunization and are at least temporarily protected from a new infection. A stable virus also makes it easier to find a vaccine.
– .
