Coronavirus: fewer people with antibodies than predicted

Coronavirus: fewer people with antibodies than predicted

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Corona: Degree of immunization lower than expected

Researchers around the world are conducting so-called antibody studies in connection with the new SARS-CoV-2 coronavirus. The results should help to provide information about the course of the disease and immunity. A study from Germany now shows that the degree of immunization is significantly lower than expected.

According to the Federal Center for Health Education (BZgA), experts assume that recovered patients have a low risk of developing COVID-19 a second time. Scientific studies have shown that people who have been through infection develop specific antibodies (the body's own antibodies) against the SARS-CoV-2 coronavirus, which can neutralize the virus in laboratory tests. However, antibodies are apparently only detectable in a few people.

Information about the current immunity status

The Medical Faculty of the Technical University (TU) Dresden and the Dresden University Hospital Carl Gustav Carus started a study in May 2020 on the spread of the SARS-CoV-2 virus in Saxon schools. The results of the first test phase with over 2,000 participants have now been published in a current communication.

According to the information, it is the largest study in Germany to date, in the context of the reopening of the schools after the lockdown, to record how many pupils and teachers carry antibodies against the SARS-CoV-2 virus and how its spread changes over time.

The numbers provide information on the current immunity status of teachers and students. They therefore provide important clues as to how school operations can continue after the summer holidays.

Antibodies only found in a few

Of the 2,045 blood samples examined, only 12 were able to detect antibodies against the coronavirus SARS-CoV-2 without any doubt. This means that the degree of immunization in the group of study participants is well below one percent (0.6 percent) and is lower than forecast.

Virus spread dynamics overestimated

The researchers led by study leader Prof. Reinhard Berner, director of the clinic and polyclinic for pediatrics and adolescent medicine at the University Hospital Carl Gustav Carus, draw a positive conclusion regarding the dynamic spread of the virus in families. So far, this has apparently been overestimated. Because in 24 families of the study participants there was at least one confirmed corona case, but only one of the test persons showed antibodies.

Schools did not become a hotspot

According to the release, there were confirmed corona cases in three of the schools examined. Nevertheless, above average antibodies were not detectable among the teachers and pupils of the institutions concerned, which suggests that the schools have not developed into hotspots.

In May and June, doctors at the Carl Gustav Carus University Hospital in Dresden examined a total of 2,045 blood samples from schoolchildren and teachers from 13 secondary schools in Dresden and the districts of Bautzen and Görlitz.

1,541 of these samples came from schoolchildren, mainly in grades eight to eleven. In addition, a total of 504 teachers participated, their ages ranged from 30 to 66 years. The proportion of male and female study participants was roughly the same among schoolchildren, while teachers dominated teachers with a share of 70 percent.

Hardly silent, symptom-free infections

According to the medical history, five study participants stated that they had previously tested positive for the SARS-CoV-2 virus. There were also 24 households in which a family member had tested positive in advance.

Doctors at the University Hospital Dresden each took five milliliters of blood from the arm veins from the test subjects. “All samples were subjected to a uniform, approved antibody test. It is suitable for automated systems and identifies antibodies to the spike protein of the SARS-CoV2 virus in the serum, ”explains Professor Alexander Dalpke, Director of the Institute of Virology at the Medical Faculty of the TU Dresden.

Antibodies could be detected without any doubt in twelve of the 2,045 samples at the Institute of Virology. In five of the twelve cases there was a known proven coronavirus infection, in seven cases the infection was not known in advance. The undisclosed number for the infection is thus just over two among the study participants.

“We are going into the summer vacation 2020 with an immunity status that is no different from that in March 2020. Of the more than 2,000 blood samples examined, only 12 were able to detect antibodies, which corresponds to a share of well below one percent. This means that a silent, symptom-free infection in the students and teachers examined by us has so far occurred less frequently than we had suspected, ”concludes Prof. Reinhard Berner.

Infections known before lockdown

It is also striking that in the 24 households in which at least one corona case was known, only one infection apparently occurred, according to which the corresponding antibodies can now be detected.

“These results of the investigation provide evidence that virus transmission in families is not as dynamic as previously thought. More than 20 of the examined subjects had at least one proven corona case in the family; however, antibodies were found in only one of these study participants, which would mean that the majority of schoolchildren did not go through an infection themselves despite an infection in the household. You also have to take this finding into account when deciding on measures to limit contact, ”says Prof. Berner.

According to the information, students from the eighth to eleventh grades were deliberately selected for the study, since they move to a greater extent independently of their parents' house and perhaps also according to the requirements of the general decree, and they also accept a correspondingly large number of social contacts . In addition, schools were deliberately selected for the study, which were known to have had SARS-CoV2 infections detected prior to the lockdown.

“Fortunately, we were able to determine that hotspots did not develop in the selected age group and in the schools examined, neither before the lockdown nor after the reopening. Four out of five students, i.e. 80 percent, stated that they had regular social contacts beyond their class group and the family. That obviously did not lead to a further spread of the virus, ”explains Prof. Berner.

A positive antibody test is not a license

The second large series of tests at the 13 schools is planned for the beginning of the new school year, and a third will take place at the end of 2020 or at the beginning of 2021 depending on the level of infection, says Professor Reinhard Berner. Together with Dr. Jakob Armann the study, while Prof. Dalpke at the Institute of Virology is responsible for the analysis of the blood samples.

Together, the scientists warned against seeing a positive antibody test as a license because the detection of antibodies does not necessarily mean protection. “In addition, there are so-called false positive results for each test, which indicate putative antibodies that are actually not available. We have therefore subjected two further tests to positive results, ”explains Prof. Dalpke.

Only those who were positive in two of the three procedures were classified as antibody carriers. According to the virologist, it is therefore crucial to take a look at the development of antibodies over the course. (ad)

Author and source information

This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.

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