Since the beginning of the year, the entire world has been concerned with a novel virus called SARS-CoV2. After the first case descriptions in Wuhan, there has been a rapid increase in the number of cases in Germany as well. In the case of a disease with the virus, the patients affected can suffer from a slight infection of the upper respiratory tract to severe lung failure and death. Since the beginning of the pandemic, an increasing number of complications such as thromboses, kidney failure and neurological damage have also been described. Interestingly, to date, children are usually less severely affected than adults, but the actual infection rates are probably similar to those of adults5 , although the actual prevalence in children is difficult to quantify and has so far been localized. The actual extent of the disease in children has also been little researched to date, and the same applies to pregnant women and their newborns.

In order to be able to understand the course of infection as well as possible and to protect the population, comprehensive testing is necessary. However, this poses great challenges for local health authorities. In addition, intensive research into possible therapy strategies and new vaccines is necessary. Here, however, the number of clinical trials in children is far behind. For adult patients, symptomatic therapies such as immunosuppressive drugs (dexamethasone) and controversially discussed antiviral drugs (e.g. ritonavir) are currently available. The medium-term goal, the establishment of a vaccine, seems to be within reach, but an exact date is not foreseeable.

In the future, in addition to the detection of the active virus by molecular diagnostic tests, the quantitative serological detection of antibodies will also be important in order to be able to make epidemiological statements about herd immunization or vaccination. An interim analysis of the SeBlueCo study showed a proportion of just 1.3% seropositive individuals among blood donors. Similar studies have already been registered and partially conducted throughout Germany. Some studies are also investigating pediatric patients, as both the routes of infection and the way the immune system deals with the virus are probably different from those in adults. Furthermore, the time course of antibody concentrations after infection with SARS-CoV2 and thus the duration of a safe immunity is much discussed. In this study, the investigators want to quantify the prevalence of SARS-Cov2 antibodies in children and adolescents during the pandemic, in order to describe the extent of antibody formation depending on various factors.

At the Children and Youth Clinic Erlangen, at least one blood sample will be taken from all inpatients and most of the patients treated as outpatients. At least one EDTA and one lithium heparin and often also one serum tube is taken. Due to the in-house laboratory, the analysis is designed for very small blood volumes. Therefore there is almost always some residual blood left in the blood tubes, which is then stored for about 7 days and only then discarded (reserve sample). For the study now planned, these residual blood samples from paediatric patients of the paediatric and adolescent clinic will serve as a basis for the analysis. The timing is such that 6, 12, 18 and 24 months after the outbreak of the pandemic in Germany, a SARS-Cov2 antibody prevalence of the local area will be determined. This will allow to investigate the local infection situation as well as the influence of a possibly available vaccination on the extent of immunization in the future.