- Countries where Omicron surged early have seen a relatively low burden of deaths so far.
- Lower population age or high vaccination coverage likely helped keep the death toll low.
- But early data suggests that the situation may be different in the US, experts warn.
It has been over four weeks since Omicron started hitting South Africa, Denmark, and the UK.
In spite of the number of infections breaking all prior records, deaths in these three countries have remained much lower than in previous waves.
Some experts have warned, however, that early data suggests the situation might be different in the US.
"The US Omicron wave is worse (for hospital admits, ICU) than what we've seen in UK, Denmark," said Eric Topol, director of the Scripps Research Institute, in a tweet Friday.
Judging from the early data, the three non-US countries with advanced Omicron waves had significant mitigating factors which the US does not share and may leave it more exposed.
"In general, outcomes appear to be far less severe than in previous waves, through a combination of an inherently milder variant, and greater protection of the population through vaccination and prior infection," Sir David Spiegelhalter, a statistician the University of Cambridge, told Insider in an email.
This is "a great relief," he said.
Here are charts for each nation to show what is going on.
South Africa: younger population
South Africa's Omicron-driven wave likely reached its peak in December, but deaths remained remarkably lower than in previous waves, as can be seen below.
The crux might be that the country "has a much younger population than Europe," said Paul Hunter, professor of medicine at the UK's University of East Anglia, in an email to Insider.
COVID-19 has generally hit older people harder, so that could explain the overall mildness of this wave, even though only 26% of people in South Africa have gotten two doses of vaccine.
South Africa's population is also thought to have had high levels of immunity from exposure in previous waves, given the poor availability of vaccines there.
The UK and Denmark: higher booster uptake
In the UK and Denmark, the death toll has also remained low.
An uptick in the last weeks could be due to delayed registration of deaths over the holiday period rather than a genuinely worsening situation, Hunter said.
Here, the low mortality could come down to the booster shots.
One study from the UK Health Security Agency (UKHSA) found that protection from two shots against hospitalization from Omicron waned from about 72% to about 52% over 24 weeks from the second dose.
But a third dose of vaccine brought that protection back up to 88%, per the study.
There is still some uncertainty as to whether that trend will continue in other parts of Europe, Hunter said.
He said deaths among people over 60 tend to lag behind cases by about a week since younger people are more likely to have seen the virus first in this wave.
US: low booster uptake, ICU rates rising
In the US, deaths haven't risen, but they haven't gone down either.
Numbers of COVID-19 patients in ICU are also rising steeply, with about 22,600 COVID-19 patients in ICU on Jan 7.
This isn't a far cry from the pandemic record high, which stands at about 28,900, per Our World In Data.
It is prompting some experts to question whether the paradigm might be different in the US.
Like Topol, Scott Gottlieb, former director of US Food and Drug Administration, noted that hospitalizations and deaths seem more pervasive than elsewhere. The "decoupling" of hospitalizations and deaths from case numbers "isn't as strong as UK, perhaps due to lower US vax/booster rates," he said in a tweet Sunday.
62% of the US population has gotten two doses, but only 22% of the whole population has gotten three. That's only about 50% of eligible adults, per Gottlieb.
Within the US, New York, Boston, and Chicago — which were all hit early on — have so far not shown strong signs of decoupling, The New York Times reported.
Director Rochelle Walensky told Fox News on Sunday the Centers for Disease Control and Prevention is keeping a close eye on deaths and that more data should give a clearer impression.