Prof. Dr. Siegbert Richard Rieg – Director of the of the Division of Infectious Diseases at the Department of Gastroenterology, Hepatology, Endocrinology and Infectious Diseases at the Medical Center - University of Freiburg – spoke with us about the new COVID-19 Variant.

 What distinguishes the 'variant of concern' called Omicron?

The omicron variant of the SARS-CoV-2 virus, first identified in South Africa and Botswana in November, has more than 30 mutations in the spike protein.  The 'variant of concern' classified by the WHO on 26th November is characterized by a significantly increased transmission rate (more transmissions with close contact) and by its ability to undergo immune evasion. The last fact means that defense mechanisms of the immune system (previous vaccinations or COVID diseases) do not protect to the same extent as against the previously dominant delta variant. The doubling of the case numbers is in the range of 2-3 days - therefore it was expected, that the omicron variant will quickly displace the last predominant delta variant.

Are there differences in the Omicron disease pattern and severity of illness?

In contrast to the alpha variant, in which fever, cough and loss of smell and taste were the predominant symptoms, an infection with the omicron variant often manifests itself as a common cold with runny nose, sore throat and headache as well exhaustion/ fatigue. Fever and cough can then develop in some time. The infection can be mild, especially in people who have been vaccinated. It remains to be seen how severe cases of Omicron will be - preliminary analysis suggests that the hospitalization rate could be lower. Nevertheless, the expected high case numbers give cause for big concern about supply bottlenecks and overwhelmed hospitals and health care systems.

What clinical consequences does this have for diagnostics and therapy?

According to the data available so far, the rapid antigen tests (lateral flow assays) and the PCR methods demonstrate a SARS-CoV-2 infection with the omicron variant with a sensitivity similar to the previous variants. However, in order to be able to differentiate between omicron and other variants, additional (mutation) PCR tests or genome sequencing have to be carried out.

If Omicron leads to more severe illnesses in patients, the immunomodulatory treatment principles (dexamethasone, possibly tocilizumab or Janus kinase inhibitors) and supportive therapies (prone position, high flow oxygen therapy, non-invasive and invasive ventilation, and possibly extracorporeal lung replacement procedures) remain unchanged. While most of the previously used monoclonal antibodies such as Bamlanivimab / Etesevimab, Casirivimab / Imdevimab or Regdanvimab lose their effectiveness (excepting preliminary data are Sotrovimab, Cigalvimab and Adintrevimab), the antiviral substances remdesivir, molnupiravir and nirmatrelvir according to their mechanisms of action are still active in vitro (independent from spike protein).

How can we protect ourselves from Omicron?

Due to the mentioned immune evasion, those who have recovered are also exposed to a higher risk of reinfection, which, however, is likely to be mild. The protection rate after a completed SARS-CoV-2 basic immunization is also significantly reduced. In both cases, a booster vaccination is the most important measure to increase protection against the omicron variant. In Germany, booster vaccinations are now recommended from 3 months after the last vaccination. The mRNA vaccine Comirnaty (Biontech / Pfizer) has now also been approved for adolescents and children from the age of 5.

In addition to the vaccination, the previous preventive measures such as wearing a protective mask (ideally an FFP2 mask), keeping your distance, general hygiene measures, regular ventilation of rooms, and frequent testing remain extremely important.