The latest research on the SARS-CoV-2 virus and its consequences.


New Omikron variant: What we have to prepare for

Portrait picture of Professor Tobias Welte.
Lung expert Professor Tobias Welte. Copyright: Tom Figiel

Stand: 16. June 2022

The omicron variant BA.5 is spreading rapidly in Germany. Federal Health Minister Karl Lauterbach declared that the feared summer wave is now a reality. He recommends that the elderly and those with previous illnesses get a booster vaccination. We asked Professor Dr Tobias Welte, Director of our Department of Pneumology.

Question: How do you see the current corona situation and for whom are booster vaccinations important now?

Prof. Welte: The risk factors for a severe COVID 19 infection are clearly different with Omikron than with the previous variants such as Delta. While in the latter, age and certain concomitant diseases such as diabetes, hypertonus and obesity played a significant role with regard to the course of the disease and mortality, this is different in Omikron. Severe courses occur mainly in immunocompromised patients. Significant risk factors exist after organ transplants, in autoimmune diseases - especially if a B-cell depleting therapy such as rituximab is administered - and in patients with haematological tumour diseases such as leukaemias or lymphomas - especially if there is a pronounced immunodeficiency due to the disease or therapy. For this subgroup of patients, a booster vaccination is recommended. However, about half of this group does not develop sufficient vaccination protection, even after a fourth vaccination. In this case, passive immunisation with an omicron-acting, long-acting monoclonal antibody can be considered.

Whether a fourth vaccination in the elderly is really useful now is controversial. In principle, there should be an interval of about six months between the third and fourth vaccination; if the vaccinations are too close together, the vaccination effect tends to decrease. Even after an omicron disease, an interval of a few months should be kept between vaccinations, if the ill person had already been vaccinated before. The decision as to whether the fourth vaccination should be given in September in order to improve immunity throughout the autumn and winter, or whether it should be given now (and then perhaps boosted again in late autumn), must be made on a case-by-case basis. I do not consider a general vaccination now to be useful.

How dangerous can subtype BA.5 be for us?

Prof. Welte: BA. 5 will lead to an increase in incidence for various reasons, mainly because of its good transmissibility. So far, we have no indication that this variant leads to more severe disease. Vaccination cannot reliably prevent infection under omicron conditions, but vaccination does prevent severe disease. Therefore, all people should have a basic immunisation (i.e. three vaccinations).

3. The infections caused by BA.5 are apparently taking place deeper in the bronchial tubes again, no longer just in the nose and throat area. Does that mean that the variant attacks the lungs more intensively and what does that mean for infected persons?

Prof. Welte: No, there is no indication for that. Basically, if shortness of breath is a leading symptom of COVID-19 disease, and especially if shortness of breath increases, the patient must be seen by a doctor.

4. What developments can we expect over the summer and into the autumn? Will the known corona protection measures be necessary again?

Prof. Welte: Because of the better transmissibility of the BA.5 variant, a certain increase in the number of cases of the disease is to be expected now, but so far there is no indication that hospitalisations or even admissions to intensive care units will increase significantly. In autumn, a stronger increase in incidence is probably to be expected. As a general rule, anyone belonging to a risk group should wear a mask in public places. And those who want to wear a mask out of their own sense of safety are of course welcome to do so. However, I do not see any justification for a general obligation to wear masks at the moment, given the low burden on the health system. It will hardly be possible to enforce this among the population. The essential question is what the goal of the Corona measures is. And that is clearly to prevent the overloading of the health service and critical infrastructure. Corona is here to stay for now, and corona infections are here to stay. A zero-COVID policy, as was still propagated until 2021, was not successful and will not be in the future. As a consequence, we have to prepare for life with corona, at-risk patients have to be protected and critical infrastructure has to be maintained. It is difficult to predict what will happen in the autumn, but if the aforementioned goals are in danger, we must be able to react quickly.

The questions asked: Vanessa Niedzella

No higher Covid-19 risk due to artificial insemination

Professor Dr Frauke von Versen-Höynck and Dr Yvonne Ziert sit in front of a special microscope for performing artificial insemination in a laboratory at the MHH Women's Clinic.
All-clear for fertility treatments: Professor Dr Frauke von Versen-Höynck (left) and Dr Yvonne Ziert have evaluated the risks for severe COVID-19 courses for pregnant women with different conception; Copyright: Karin Kaiser / MHH

Research team analyses data from SARS-CoV-2-positive pregnant women.

Stand: 25. May 2022

If pregnant women become infected with the SARS-CoV-2 coronavirus, they are more likely to suffer from severe COVID-19 compared to non-pregnant women. Expectant mothers are therefore more likely to require intensive medical care in hospital. In addition, the risk of premature births and stillbirths increases, as well as complications in the newborns, who consequently have to be cared for in a neonatal intensive care unit. However, the method of conception - whether natural or medically assisted - does not seem to play a role. This is the result of a study led by Professor Dr Frauke von Versen-Höynck, senior physician at the Department of Obstetrics and Gynaecology at the Hannover Medical School (MHH) in cooperation with the University Hospital Schleswig-Holstein (UKSH) at the Kiel Campus. The results of the multi-centre study have now been published in the American Journal of Obstetrics and Gynecology, one of the world's most important specialist journals in gynaecology.

CRONOS register as data basis

For the study, the researchers compared the pregnancy histories of 1485 SARS CoV 2 positive expectant mothers from about 100 German maternity hospitals across Germany. The data came from the so-called CRONOS register for assessing the risk of corona infection for pregnant women and their newborns. Patients who tested positive in the clinic during their pregnancy were observed - from the course of the postpartum period until six weeks after birth. "Since the beginning of the pandemic, we have seen a great deal of uncertainty among women who rely on the help of reproductive medicine to become pregnant," says Professor von Versen-Höynck, head of the Reproductive Medicine and Molecular Perinatology Unit at the MHH Women's Clinic. "We therefore asked ourselves in this study whether there is an additional increased risk for these women with a coronavirus infection compared to pregnancies after spontaneous conception."

Higher risk of complications has other causes

In order to be able to set this special focus, the finished data tables from the Cronos register first had to be processed in a complex way. The necessary programme codes were developed by Dr. Yvonne Ziert, research assistant at the MHH Institute of Biometry and first author of the study. "The special thing about this project for me was the very close cooperation with the doctors," the scientist reports. "They provided the medical hypotheses, and I prepared the data so that they could be answered precisely." The result: it is true that the risk of obstetric and neonatal complications is higher in pregnancies after medically assisted conception. "However, this is due to corresponding pre-existing conditions such as diabetes, obesity and high blood pressure, a higher age of the pregnant women or multiple pregnancies, which are mainly found in this group of expectant mothers," Professor von Versen-Höynck emphasises. However, the type of conception is not a risk factor for a severe course of COVID.

Influence of vaccination still unclear

Next, the research team would like to look at the influence of vaccination. "The data still come from the first pandemic phase, when there was no vaccination recommendation for pregnant women," explains the senior physician. In the meantime, however, the Cronos register already contains the data of more than 1000 vaccinated expectant mothers. "It is to be expected that the prognosis for these women will be much more favourable," she assumes. But one thing is already certain: the all-clear can be given for fertility clinics even in times of pandemic.

Keyword CRONOS: The CRONOS register study was initiated by the research network of the German Society for Perinatal Medicine (DGPM) under the direction of Professor Dr. Ulrich Pecks (UKSH, Campus Kiel) and Professor Dr. Mario Rüdiger (University Hospital Dresden). The aim is to research the effects of a SARS CoV 2 infection on the health of mothers and their newborns. With the data obtained in Germany, the DGPM wants to give doctors a basis for treating and advising affected patients.


New visiting regulations for relatives

From Monday, 28 February 2022, visits by relatives will be easier

Stand: 24 February 2022

The ban on visits to the Hannover Medical School (MHH), which has existed since 1 December 2021, has been lifted. From Monday, 28 February 2022, the following visiting regulations will apply:

  • One visitor per day for one hour in the period from 2 pm to 7 pm is possible
  • Visits must be registered at the Service Points
  • All visitors need a current test with official certification from a recognised testing centre. Without negative test results, unfortunately, no visit is currently possible!
  • There are no test options at the MHH

In the delivery room, in the children’s hospital and for relatives of patients receiving palliative care or dying patients as well as patients suspected of an approaching phase of death, the existing derogations continue to apply.

For more information, please visit

How a SARS-CoV-2 infection can become severe COVID-19

Two women in white coats and mouth-nose protection hold several small vials in their hands.
Professor Dr Christine Falk (right) and her research assistant Louisa Ruhl have investigated how a severe course of COVID-19 occurs. Copyright: Karin Kaiser/MHH

Research team demonstrates role of inflammatory plasma proteins in blood vessel dysfunction.

Stand: 03. Februar 2022

Infection with SARS-CoV-2 leaves some people almost unaffected, while others develop a life-threatening covid-19 disease. It is not yet known why the courses of the disease differ so much. A team of scientists led by Professor Dr Christine Falk, head of the MHH Institute for Transplantation Immunology and a scientist at the German Centre for Infection Research (DZIF), has now discovered that, in addition to strong immune activation and inflammatory reactions, a functional disorder of the vascular system plays an important role in severe courses. The results have been published in the journal Signal Transduction and Targeted Therapy.

Endothelial barrier no longer active

Of particular importance is the so-called endothelium, a thin layer of cells that line the blood vessels and thus form a barrier between blood flow and tissues. In severe COVID-19 courses, this barrier between the alveoli and the surrounding vessels is no longer intact. "In our study, we investigated which immune cells are activated in severe cases and in what way the endothelium, i.e. the blood vessels, and their activation play a role in the disease process," explains Professor Falk. In the immune system, there is an excessive activation of T-lymphocytes and natural killer cells (NK cells), as well as the development of memory T-cells and a strong increase in plasmablasts - these are cells that can produce large amounts of antibodies.

Plasma proteins as possible biomarkers

In studies on 58 patients with severe COVID-19 and 28 recovered patients in intensive care, the research team was able to prove that the severity of the disease is linked to the disruption of the endothelial barrier and can also be measured using inflammatory plasma proteins. A pattern of seven plasma proteins appears to be associated with severe disease characterised by strong inflammatory processes and sustained damage to the endothelium. Furthermore, recovery from severe COVID-19 cases seems to be related to the regeneration of this endothelial barrier. "We were able to show that COVID-19 intensive care patients can be divided into different groups based on their plasma protein profile, which are associated with the severity of the disease," explains first author Louisa Ruhl, a natural sciences PhD student at MHH. This finding is of great importance for the identification of potential biomarkers for severe COVID-19 courses, as well as for the development and use of new therapeutic approaches.

Which immune cells lead to the damage?

The research team now wants to find out which players of the immune system lead to activation and damage of the endothelium and whether the strong activation of the immune system also leads to the development of virus-specific T-lymphocytes, which can recognise and destroy infected cells and thus contribute to overreaction. In addition, the study has shown that there are also shifts in the immune cell repertoire in recovered COVID-19 intensive care patients. This could also be related to the development of long COVID diseases.

The study is a cooperation with the Clinic for Pneumology Dlinic for Pneumology, the Clinic for Gastroenterology, Hepatology and Endocrinology, the Institute for Virology, the Deutschen Zentrum für Lungenforschung (DZL), the Zentrum für Individualisierte Infektionsmedizin (CiiM), the Cluster of Excellence RESIST and the Universitätsklinikum Erlangen

You can find the original publication „Endothelial dysfunction contributes to severe COVID-19 in combination with dysregulated lymphocyte responses and cytokine networks” here.