Omicron emerged as a variant of concern only in November 2021, but all the mutations it contains except one had been described before that.
Researchers at the Federal University of São Paulo (UNIFESP) in Brazil, supported by FAPESP, 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 in January 2022.
"In light of the data available so far, we believe the existing vaccines are indeed effective against all variants of the virus, all things considered. They may also be effective against any other variants that emerge in future," said Ricardo Durães-Carvalho, last author of the article. Durães-Carvalho is a researcher affiliated with the university's medical school (EPM-UNIFESP) and has a scholarship from FAPESP.
In October 2021, before the World Health Organization (WHO) recognized the emergence of omicron, another study led by Durães-Carvalho described several mutations shared by a number of variants. A paper on the topic is published on the preprint platform medRxiv (not yet certified by peer review).
The group analyzed more than 200,000 genomes of SARS-CoV-2 and other human coronaviruses. They found identical mutations in different strains, which could serve as targets for future vaccines.
"Omicron corroborates our study. Out of 35 mutations in the variant's spike protein [used by SARS-CoV-2 to bind to a specific receptor when infecting human cells], only one was unknown. Twenty-five were in RBD [receptor-binding domain] 15 and RBM [receptor-binding motif] 10, regions of the virus that bind to human cells and are therefore potential targets for neutralizing antibodies," Durães-Carvalho said.
"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, as can be seen by comparing this new wave with previous waves that occurred before there were vaccines or when a smaller proportion of the population had been fully immunized," said Robert Andreata-Santos, first author of the Letter to the Editor in JMV. Andreata-Santos is a postdoctoral fellow at EPM-UNIFESP with a scholarship from FAPESP.
The researchers stress that the article is based on the data currently available on omicron and on the genomes of other variants sequenced so far. As the pandemic proceeds and more data is collected, it may be possible to confirm their hypotheses.
