Brazilian researchers have found that Omicron has mutations detected in previous variants and that is the reason why it is less severe among the vaccinated.

Researchers at the Federal University of Sao Paulo (UNIFESP) in Brazil attribute this factor to the effectiveness of the existing vaccines against the variant, reflected in the relatively small number of severe cases and deaths despite Omicron's heightened transmissibility.

The hypothesis is raised in an article by the scientists published in the Journal of Medical Virology (JMV) as a Letter to the Editor.

Before the emergence of Omicron, a separate study led by Duraes-Carvalho described several mutations shared by a number of variants.

The group analysed more than 200,000 genomes of SARS-CoV-2 and other human coronaviruses.

In the paper published on the preprint and not yet peer-reviewed, the team found identical mutations in different strains, which could serve as targets for future vaccines.

"That may explain why vaccination has so far been effective even though none of the vaccines on the market was designed specifically for Omicron. They don't prevent transmission, but they prevent severe cases and deaths," Robert Andreata-Santos, postdoctoral fellow at EPM-UNIFESP wrote in the JMV.

In the study posted to the pre-print platform, Duraes-Carvalho and the team analysed the dynamics of viral dissemination and evolution over time in Brazil, the US, and India, for the period between February and August 2021.

The analysis showed an increase in the number of mutation sites in the viral genome, above all in the spike protein, configuring what the researchers term 'convergent evolution'.

This means that different variants undergo identical mutations that confer advantages such as evading the host's immune system or binding more efficiently to human cells.

With the spread of the Delta variant, more spike protein mutations were observed, as well as signs of recombination, one of the factors that can lead to the emergence of novel variants.

In December, the researchers analysed 146 Omicron-genome sequences from Australia, Austria, Belgium, Botswana, Canada, England, Germany, Hong Kong, Israel, Italy, and South Africa.

Evidence of recombination was found when sequences from Beta, Delta and Omicron were aligned, suggesting that co-circulation of several variants may enhance recombination events.

(This story was published from a syndicated feed. Only the headline and picture have been edited by FIT.)