Calibrating Omicron’s Risk

Here is the carefully accurate current assessment of omicron by the CDC.

In South Africa it is very clear that omicron is spreading more rapidly than any prior variant. There is growing evidence that omicron’s ability to evade prior immunity is resulting in a higher incidence of reinfection and breakthrough infections.

There is accumulating evidence that similar omicron transmission speed is being experienced in Denmark and the United Kingdom (more), each with vaccination rates better than most places (including the United States).

As experienced with every prior version of covid, in the vast majority of omicron infections so far, disease symptoms are mild. One rigorous study found that 2.1 percent of those infected with the Sars-CoV-2 virus have required hospitalization.

With every prior version of covid, as more people are infected with omicron, the number of those experiencing severe disease has also increased. So, for example, a surge in delta-related hospitalizations is currently stressing the US health care system. Delta is not as contagious as omicron, but it is more efficiently transmissible than previous variants. This eventual surge in hospitalization has been predictable and predicted.

Please consider this word problem:

Your locality has a supply of 100 staffed and otherwise clinically supported hospital beds.

The incidence of covid-related disease requiring hospitalization is two-percent.

What number of covid-related infections can your local hospital capacity support?

There is a largely fixed supply — expensive, difficult, and time-consuming to adapt — encountering surging and volatile demand.

Hospital bed capacity (per 1000 persons) is very similar in the United States (2.8), United Kingdom (2.4), and Denmark (2.6). I would not be surprised to learn that US capacity has fallen over the last year because of covid-related staffing constraints.

Some say, without much evidence yet, that omicron’s severity is half that of delta. So far there is increasing evidence that omicron may be four times as contagious as delta. Both estimates are early, but still: do the math. Where does this leave us in terms of probable proportions experiencing severe disease?

Two Fridays ago I was frustrated by the knee-jerk fearful reactions to initial reports of omicron (here and here and here). This Friday I am as concerned by the lack of attention to accumulating evidence of risk. The virus is changing, but its behavior is stolidly predictable compared to erratic social, political, and financial responses to the virus.

Risk is an outcome of how threat interacts with vulnerability. The same threat can produce dramatically different consequences, depending on what vulnerability is encountered. This is obviously true in terms of individual covid consequences. It may be less obvious but as true in how different social groups (local to global) respond to the threat of covid. Early, diligent demand-management (e.g., Israel) reduces vulnerability and can avoid flood or drought of flows. Inconsistent or absent demand management increases vulnerability while amplifying extreme gyrations of supply and demand.


December 11 Notations:

Sometime yesterday, Anjana Ahuja posted “The Omicron Paradox is Starting to Reveal Itself” in the Financial Times. She does a better job offering the same argument as above. Many Brits are concerned that omicron is hurtling toward very high case counts by Christmas. In at least two prior waves, the USA has tracked the UKs demand curve about 4 weeks later. Given current delta-driven demand for medical care in the United States, such a one-two punch would be especially punishing.

Early today (Saturday), Bloomberg posted a helpful round-up on what is known and not-yet-known related to omicron.

Later on Saturday: “New modelling from the London School of Hygiene & Tropical Medicine (LSHTM) suggests the Omicron variant has the potential to cause a wave of transmission in England that could lead to higher levels of cases and hospitalisations than those seen during January 2021, if additional control measures are not taken.” Even the most optimistic projections are sobering. (More)