Abstract
In January of 2021, much of the world was dealing with the newest severe acute respiratory syndrome coronavirus 2 variant, Delta. As 2021 went by, it was clear that the Delta variant was worse than its predecessors were, but we seemed to know the enemy by then, and life was starting to feel somewhat normal in many places. By the end of 2021, we were unfortunately introduced to the newest member of the variant of concern (VOC) family, the Omicron variant, and we found ourselves again asking those familiar three questions about transmission, vaccine effectiveness, and disease severity.
Before the first days of 2022, it was clear that the original interest and concern around this variant was well justified because it was proving to be the most difficult variant to handle yet. It did not take long to get answers to the three main questions we ask about new VOCs. There have been different estimates regarding comparative transmission rates of the Omicron VOC, but where the Delta variant took ∼6 months to go around the world, Omicron did it in <2 months. This is not surprising given the long list of spike protein mutations it has in common with the other variants, giving it the “faster spreader” superpower.
Regarding the “antibody escape” superpower, it is also clear that, as predicted from its mutational profile, the Omicron variant can break through immunity induced by vaccination and/or natural infection even better than all other VOCs. Having said that, the variant seems to easily infect individuals with vaccine-induced immunity or immunity derived from natural infection, but this immunity, at least in most infected individuals, seems to be able to limit the virus to a mild infection.
The biggest question around the Omicron variant was whether or not it would be associated with mild disease, as was originally suggested, and the answer to this question is still complicated and debated. The problem lies in the fact that original cases of Omicron infection appeared to be mild, but were they mild because the variant itself is less pathogenic, or because the population it was infecting had pre-existing immunity from vaccination and/or natural infection? Properly answering this question will require variant phenotyping experiments that are surely ongoing already, but it is clear that Omicron infection is not mild in everyone, as we have seen severe illness and death caused by this variant already in some infected individuals.
Unfortunately, the early labeling of the Omicron variant as “mild” might have contributed to many individuals not taking this variant as seriously as they had others, and this has had dire consequences for many people as hospitalizations and deaths are presently rising in many places. The silver lining in this wave is that whatever the cause, be it lower pathogenicity of the variant, protection from severe disease by pre-existing immunity, or a combination of both, the death rates seem to be lower in this wave than they were in previous waves.
This has to be at least, in part, due to the availability of vaccines. Of course, it is important to note that the disconnect between cases and deaths was already present in highly vaccinated regions of the world even when the Delta variant was dominant, meaning the mildness of Omicron infections might be more attributable to pre-existing immunity than to characteristics of the variant itself.
In closing, there are still many questions to be answered about this newest VOC, and scientists around the world are not faltering in their diligent pursuit of the answers to these questions. Someday we will look back and marvel at all that was learned in such a short time.