Corona infection numbers – is there a threat of flying blind in the Omikron wave?

A blood sample that tested positive for the omicron variant of the corona virus. (imago images / Christian Ohde)
The epidemiologist Hajo Zeeb from the University of Bremen wants to be prepared for what is to come: “You shouldn’t dwell on the incomplete numbers and say: OK, we’ll wait for that to be more precise. That doesn’t help us any further, we also have to see what happens. “

To do this, the expert now looks at the available data and tries to obtain as much information as possible about the Omikron variant from it. This is currently not going so well in Germany because the variant is – still – relatively rare. Hajo Zeeb is therefore looking closely at countries like the United Kingdom or Belgium, where the new variant has been around for a long time.

It is helpful to take a look abroad

For example, he is interested in why the number of infections at Omikron is increasing so much faster: Is that because it is more infectious or because there are indications that this immune escape is taking place – i.e. the omicron variant bypasses an existing immune protection? Which part is which of it? Then I’ll look, but there are some indications that it’s a solid mix of both. “

Hajo Zeeb can only investigate the details because the British report new figures on suspected Omikron cases every day. Helmut Küchenhoff from the statistical consulting laboratory at the University of Munich would therefore like to see incidence figures broken down by virus variants in Germany as well. Because the different variants of the virus that are currently in circulation are spreading at different speeds. If they are summarized in an incidence value and you do not know which proportion has which variant, then you cannot assess the actual influence of the variants on the infection process.

Incidence figures for individual virus variants provide more insight

If you had a solution for variants and knew that this is the rate of increase of Omikron, that is the rate of increase of Delta, you would see more clearly, says Helmut Küchenhoff: “Then I can extrapolate better and assess the situation. That is a sensible strategy, yourself to look at that separately. “

But these data are not available for Germany. Helmut Küchenhoff would also like to see figures on vaccination breakthroughs in hospitals in order to better assess Omikron. This data in turn should actually be reported, but is incomplete. In his opinion, one should now look primarily at the number of Corona hospital admissions: “We are of the opinion that the hospitalization indicator is becoming more important at Omikron, because at Omikron you are uncertain that you do not know how difficult the processes are Comparison to the incidence. “Because the hospitalization incidence is not affected by an unreported figure and represents the burden on the health system and the population, says the statistician. But it is also true: It lags behind reality by weeks in some cases because of the way in which it is recorded and the long reporting channels.

Nowcasts are intended to circumvent the delay in reporting

To get around this problem, Helmut Küchenhoff and his colleagues calculate so-called nowcasts: models that estimate the actual, current hospitalization rate. So far, they have worked almost perfectly. But will it stay that way in the face of Omikron? Helmut Küchenhoff is optimistic: “The model is flexible. There are trends in it and that is why we are optimistic that we can do this pretty well with our models at Omikron too. “

The nowcast is far more up-to-date than the bare numbers on hospitalization. Nevertheless, heads of government often refer to these bare numbers in their decisions. Most recently in November, when the federal-state round made corona measures dependent on it. It turns out that the indicators that the scientists calculate are only worth something if they are also taken into account in the public discussion and in political decisions.

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