Preliminary evidence from South Africa suggests the Omicron variant is highly transmissible and is more capable of causing infections in vaccinated people. There is also evidence of the Omicron variant causing reinfections, suggesting naturally acquired immunity is also less effective against the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Since the genomic surveillance efforts of South African scientists that led to the discovery of Omicron, public health officials are reporting cases of Omicron around the world, including Germany and the United Kingdom. Researchers from Italy who had previous models forecasting SARS-CoV-2 transmission published a study on the preprint server medRxiv* forecasting coronavirus case rates with the arrival of Omicron.

Study: Forecasting COVID-19 infection trends in the EU-27 countries, the UK and Switzerland due to SARS-CoV-2 Variant of Concern Omicron. Image Credit: benjamin poturak/Shutterstock

The Omicron variant was identified in South Africa in late November and is predicted to be more infectious than previous variants of concern. Omicron has more than double the number of mutations on its spike protein than Delta. Some of these mutations are known to evade the immune system, weakening the effectiveness of neutralizing antibodies.

Current forecasting results suggest that Omicron will cause a surge in COVID-19 cases across many European countries. In the worst-case scenario, there can be a 2.03-fold or 200% increase in daily cases, despite high vaccination levels in most regions.

The researchers stress the need for public health interventions focused on limiting the spread of COVID-19 transmission, including social distancing, face masks, and indoor ventilation.

Modeling details

The researchers used previous modeling algorithms to predict how the Omicron variant will spread across 27 countries in the European Union, the United Kingdom, and Switzerland along with the number of daily and weekly COVID-19 cases.

They first based their data from existing epidemiological trends regarding Omicron transmission in South Africa. These trends began in the first that 17 days South Africa reported the Omicron variant.

If trends followed an asymmetrical sigmoidal curve following a parametric growth, then researchers could estimate the number of new COVID-19 infections in South Africa through the end of 2021.

With the Omicron outbreak in South Africa, the best-case scenario is 80,000 daily COVID-19 cases. The worst-case scenario is 120,000 daily cases.

Projections of COVID-19 cases in Europe

The researchers then used these trends and modeled it to the rate of COVID-19 cases in the European Union, the United Kingdom, and Switzerland. They estimated a downward trend after an initial peak of infections — though it did not initially contain the impact Omicron has on infection rates. Afterwards, they added cases based on the estimated on number of individuals at risk of infection in South Africa.

The researchers predict a surge of coronavirus cases in early 2022 in 27 European Union countries, the United Kingdom, and Switzerland.

Without Omicron, there is an expected 145,000 daily coronavirus cases by January 15, 2022. But this number increases with the introduction of the Omicron variant. The best-case scenario is 375,000 cases while the worst-case scenario is 440,000 daily cases.

Therefore, Omicron might represent a relative increase from the background daily rates of COVID-19 infection in Europe of 1.03-fold or 2.03-fold, that is up to a 200% increase”

, explained the researchers.

The rise in cases is already underway. Denmark has rigorous SARS-CoV-2 testing requirements and is considered a leader in genomic sequencing of SARS-CoV-2 variants of concern. However, Omicron cases have increased in the area, and recent reports suggest a doubling of new cases every second day.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Jocelyn Solis-Moreira

Jocelyn Solis-Moreira graduated with a Bachelor's in Integrative Neuroscience, where she then pursued graduate research looking at the long-term effects of adolescent binge drinking on the brain's neurochemistry in adulthood.