Researchers reveal Omicron’s extraordinary ability to evade the immune system

The current wave of COVID-19 highlights a particularly high risk of reinfection with the Omicron variant of SARS-CoV-2. Why is this? A team from the Center for Emerging Viral Diseases at the University of Geneva (UNIGE) and the University of Geneva Hospital (HUG) analyzed the antibody-neutralizing capacity of 120 people infected with the original SARS-CoV-2 strain or one of them. Alpha, beta, gamma, delta, zeta, or omicron (subvariant BA.1) variants. And unlike its predecessor, Omicron appears to be able to evade antibodies produced by all other mutants. Vaccinated individuals also have a reduced ability to neutralize, but are far superior to innate immunity alone. This may explain why Omicron is involved in the net increase in vaccine breakthrough infections, but not in hospitalization.These results can be read in the journal Nature Communications..

Since the beginning of the pandemic, the HUG Outpatient Testing Center has provided the SARS-CoV-2 testing to the community. “As a national reference center for new viral diseases, we have the ability to sequence the majority of positive cases to monitor the emergence of new variants,” said professor of medicine at UNIGE School of Medicine. Isabella Eckerle explains. The HUG-UNIGE Center for Emerging Viral Diseases, which led the study, “collected samples of the original virus and all its variants that emerged in Switzerland from the beginning of 2020. The rarest viruses such as gamma and zeta. It also includes a comprehensive collection of samples from individuals with different infection backgrounds, according to the same protocol. “

The research team collected blood samples from 120 volunteers who were previously infected with one of the different variants, either unvaccinated or vaccinated and infected, before or after vaccination. “Because the average age is 28 to 52 years, there are no major comorbidities, and there is mild to moderate COVID-19, this cohort accounts for the majority of community cases,” Isabella Eckerle said. I will explain.

Vaccination increases antibody levels 10-fold

The goal was to determine how well the antibodies produced during the initial infection could neutralize the various variants of SARS-CoV-2. “Omicron has proven to be the most effective in avoiding existing innate immunity, but vaccination-induced immunity is less so,” said the Vaccination Center of the Faculty of Pathology and Immunology. Benjamin Meyer, a researcher at, explains. University School of Medicine. Indeed, antibody levels against ancestral SARS-CoV-2 in vaccinated people are approximately 10-fold higher than those who have only developed post-infection immunity. In addition, the combination of the two, known as hybrid immunity, appears to maintain higher and broader reactive antibody levels.

“Therefore, Omicron can circumvent existing immunity and cause infection, but even after vaccination, COVID-19 hospitalization and mortality are reduced in Omicron as well.” Nevertheless, SARS-CoV- 2 retains an amazing ability to mutate, which also appears to be accelerating. “Visirance is still needed, especially since the epidemic curve has risen sharply since the advent of the latest Omicron subvariant, BA.5,” adds Isabella Eckerle.

Scientists also performed antigen mapping of various mutants based on the same model used to determine influenza antigen changes.

This calculation method can represent the distance between the antigenic features of the mutants involved. The farther they are, the less effective the antibodies produced during the previous infection. Similar to the rapidly disappearing Zeta mutant, the serotype of Omicron was found to be quite different from other serotypes. “

Meriem Bekliz, a postdoctoral fellow in Isabella Eckerle’s lab and the lead author of this study.

Advances in virus understanding

The respiratory virus has never been so scrutinized. “This virus, which belongs to the same family of coronaviruses that cause almost one-third of the common cold, can spread like a wildfire in a non-immune population that fights it,” Benjamin Meyer said. Explains.

“Currently, there are sequencing and molecular observation tools that were unknown a few years ago. The discoveries we are making today open up useful perspectives and understandings that go far beyond SARS-CoV-2.” COVID- The 19 pandemics have also enabled unprecedented acceleration in vaccine research. Currently, several teams are working on nasal spray vaccines. It is easy to administer and can act directly on the most useful mucous membranes of the nose and throat, among others.