There is increasing evidence that the Omicron Covid variant is more infectious but less deadly than previous versions. Researchers believe this variant attacks mainly the throat but spares the lungs, in contrast with the Delta and other variants.
The latest mutation has likely altered how the virus can infect different types of cells. The new variant seems more capable of infecting the upper respiratory tract —in other words, the throat— rather than cells in the lungs. This would also explain why it spreads more easily: a virus that attacks the throat is easily transmissible but less deadly than a virus that attacks the lungs, which can be potentially much more dangerous. These are very preliminary studies and need further confirmation.
A team from the University of Liverpool published a pre-print showing how the Omicron variant is 100-fold less severe in mice. In this study, mice infected with this variant lost less weight, had a lower viral load, and experienced milder symptoms. In addition, animals recovered faster, which seems to tie with recent clinical data for people infected with Omicron.
A second study from the University of Belgium found similar results: Infected hamsters had a lower viral load with Omicron than other variants, likely because the virus infected only the upper respiratory tract and caused a less severe disease.
Results from a third study from the University of Glasgow offer a possible explanation for this milder version of the disease. It seems that the Omicron variant not only changed the type of cells it attacks but it also changed the way in which it attacks these cells. Worryingly, although it seems less dangerous than other variants, these changes mean the virus can evade the immune system, and vaccines may no longer be as effective as before. The good news is that a booster dose gave a partial restoration of immunity. For the Glasgow-based researchers, this means that Omicron-specific vaccines may be required, either directed at the general population or vulnerable groups.
Given these changes with the Omicron variant, there is ongoing debate regarding the best place to take samples for Lateral flow tests: continue with nasal or switch to the throat? There is some anecdotal evidence that nasal samples alone may not be effective in detecting positive cases of Omicron, and research groups are working hard to determine the best way to test for this variant.