Whether Omicron, the fifth WHO-designated variant of concern, will transmit more effectively than Delta, the fourth VOC, might best be considered in the context of how much transmission of Delta is occurring in South Africa now compared with in Europe.
To create a rough analogy, Delta is the global heavy-weight boxing champion of SARS-CoV-2/COVID-19, and Omicron is the latest contender for the title of COVID champion. With little Delta transmission now in South Africa, it is as if Delta-the-champion was already stepping out of the boxing ring for multiple reasons, just as Omicron-the-contender entered and quickly dominated since the start of this month in the near-empty ring.
In much of Europe (and the USA), however, Delta is still being widely transmitted. Thus, Delta-the-champion VOC is still strong in these geographic arenas (rings), so Omicron-the-contender VOC could have a much more difficult fight to defeat Delta and dominate transmission in the months ahead than it has so rapidly this month in South Africa.
Clearly, this is not a perfect analogy, e.g., the relative frequency and severity of “vaccine breakthrough infections,” reinfections and monoclonal antibody resistance could well differ between Omicron and Delta.
Other key considerations for Omicron versus Delta are:
- Frequency of asymptomatic transmission;
- Frequency and severity of “long COVID”;
- Frequency and severity of MIS-C;
- Frequency, severity and contagiousness of infection in 0-25 year olds.
Finally, although we all dread the thought, the next-up Greek letters for variants are “Pi” and “Rho.” Even if they are not “variants of concern,” there will likely be a sixth VOC that follows Omicron, Delta, Gamma, Beta and Alpha … absent accelerated global vaccine equity and implementation.