Coronavirus explainer: How Omicron dodges the immune system and evades antibodies in vaccinated and unvaccinated people

Omicron infection generally causes less severe disease in comparison to the infection caused by prior variants. However, some people may still get severe disease, require hospitalization, and could also die due to the Omicron variant. Even though the infections are less severe, an increasing number of cases can overwhelm the healthcare system.

The researchers from the Geneva University’s Centre for Emerging Viral Diseases and the Geneva University Hospital, have revealed the exceptional capacity that the Omicron variant has to evade our immunity. The findings were published in the journal Nature Communications.

Increase in the variants’ transmission can result from biological changes that speed up infection, allowing the virus to infect more people at a faster rate. However, according to researchers, the rise of cases due to new variants BA.4 and BA.5 seems to stem from their capacity to infect people who were immune to previous forms of Omicron and other variants. The sizes of BA.4 and BA.5 waves will vary from place to place.

In this study, the researchers analysed the antibody neutralisation capacity of 120 people infected with the original SARS-CoV-2 strain, or with the Alpha, Beta, Gamma, Delta, Zeta or Omicron (sub-variant BA.1) variants.

The volunteers of the study included both kinds of people who were unvaccinated or vaccinated and also got infected either before or after their vaccination. The mean age of the participants was between 28 and 52 years and they mostly experienced a mild to moderate form of COVID-19.

The aim of this research was to find out how well the antibodies generated during the first infection were able to neutralise the other different variants of SARS-CoV-2. Here’s what they discovered.

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The researchers found that unlike its predecessors, the Omicron variant is able to evade the antibodies previously generated by all other variants. Still, the infections result in less hospitalisations as the researchers found that the vaccinated individuals’ neutralisation capacity, even if it was reduced, remains far superior to natural immunity alone. Researchers suggest that vigilance is required, especially as the epidemiological curves have been rising since the appearance of BA.5.

Lab studies suggest that antibodies triggered by vaccination are less effective at blocking the new BA.4 and BA.5 variants, than they are at blocking earlier Omicron strains. This means that even vaccinated and boosted people are vulnerable to multiple Omicron infections. Even the antibodies of people with hybrid immunity – from vaccination and previous Omicron BA.1 infection – struggle to incapacitate BA.4 and BA.5 variants.

According to research, antibody levels against ancestral SARS-CoV-2 in vaccinated people are roughly 10 times higher than in people who have only developed post-infection immunity. Moreover, hybrid immunity seems to maintain higher and broader reactive antibody levels. Without vaccination and other preventive measures, coronavirus can spread like wildfire in people with no immunity to fight it.

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SARS-CoV-2 virus retains an astonishing ability to mutate. Scientists, doctors and other healthcare workers are learning and discovering new things about the virus with time. The coronavirus pandemic has led to an unprecedented acceleration in vaccine research. Currently, several teams are working on nasal spray vaccines, which are easier to administer and can act directly in the mucous membranes of the nose and throat.