Katherine J. Wu: Why don’t we yet know for sure how worried we need to be about Omicron?

Boghuma Kabisen Titanji: What we do know about the variant is this: Some of its spike-protein mutations have been seen in other variants and other lineages described earlier on in the pandemic, and have been associated with increased transmissibility and the ability of the virus to evade the immune response. What we don’t know, and what is really hard to predict, is what the combination of mutations will do together. This particular variant now appears to be outcompeting other circulating variants in South Africa—there have been these clusters of cases. That is actually what led to this variant being identified in the surveillance systems that they have in place there. That raises the concern that the variant is more transmissible or may be escaping the effects of the immune response induced by vaccines or infection from earlier strains. But we really don’t know that for sure yet.

The disconnect is this: The surveillance systems have worked exactly in the way they are designed to. It makes us know what to look out for. However, when these systems pick up a signal, we don’t immediately get the epidemiologic data we need to know all of the impacts a new variant can have. That takes time. Right now, we have a limited number of [viral genomic] sequences, and a limited number of cases. Now the alert is out. People will start looking for this new variant, not only in the countries that initially reported on this, but now worldwide. There’s now a search to make sure this variant is well-characterized. That’s when we will gain a better understanding of whether it’s causing more severe disease, how much it is escaping immunity, and how transmissible it is.