Interesting early data on #omicron severity in this preprint from SAfrica.

Main take-away for me still:
Population with high protection from severe disease but low protection from infection means more infections with mild symptoms.
Inherently milder? 🤷‍♂️

medrxiv.org/content/10.110…
The authors compared SGTF cases with non-SGTF cases during the same time period (1/10 - 30/11).

Remember: SGTF is S gene target failure, the signal in certain PCR tests that is currently used as an (imperfect) proxy for omicron infections.
The authors found that the risk of these likely #omicron cases to end up in hospital was only about one fifth the risk (10-30%) of cases without SGTF (likely not omicron)
But once patients were in hospital, their risk of severe disease was about the same.
Interestingly, the authors also compared risk of SGTF cases now with risk of Delta cases in the previous wave (April to November).
Here they found something else:
Hospitalized #omicron cases had about 30% (20-50%) the risk of hospitalized Delta cases of severe disease.
Why the difference:
Most likely explanation would seem that population immunity post-Delta has lowered risk of severe disease over all. So hospital outcomes are better now for all infections whether #omicron or not.
And why fewer hospitalizations with #omicron?

Omicron‘s immune evasion means more infections in vaxxed/recovered and those are more likely to be mild

Of course, omicron could also be inherently milder. It‘s just too early to tell with any certainty.
This is what the authors write:
„It is difficult to disentangle the relative contribution of high levels of previous population immunity versus intrinsic lower virulence to the observed lower disease severity.“
The difference when comparing cases in same time period vs. comparing with earlier wave „suggests that this reduced severity may be in part a result of high levels of population immunity (due to natural infection and/or vaccination)“
Remember that this is still early data with lots of limitations and caveats.

More data to come from UK soon, so picture will become clearer over time…

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More from @kakape

21 Dec
"We are clearly in a new and troubling phase of this pandemic. What we have seen so far is sobering but there is still much to learn about Omicron. We cannot afford to cross our fingers and hope this crisis blows over”, @JeremyFarrar writes in a statement just out.
@JeremyFarrar If transmission isn’t slowed, "we could see profound impacts on health systems but also across sectors such as education, hospitality, public transport, police and essential national infrastructure as infections prevent people from working.".
@JeremyFarrar It's "staggering and deeply frustrating that two years into this pandemic – when we have gathered so much evidence and made huge scientific progress – that governments are still not anticipating events and acting early or working together anywhere near the scale that is required"
Read 5 tweets
21 Dec
Gemany’s @rki_de (basically our CDC) just put outs its recommendations for measures to curb #omicron.

Background: Number of delta infections and hospitalisations are declining, but #omicron cases are currently doubling about every 3 days and ICUs still very full.
@rki_de They recommend immediately:
- continuous masking indoors (and outdoors if <1,5 m distance), incl. for vaccinated people and in schools
- closing all bars, clubs, restaurants (except for takeaway), indoor sports
- cancelling large events
@rki_de - 2G+ for cultural events etc (so vaccinated or recovered, and test needed)
- 2G in most shops (only vaccinated or recovered allowed)
- 3G in supermarkets etc (so test needed for those not vaccinated or recovered)
- no singing indoors (for instance in church)
Read 4 tweets
20 Dec
You must all be tired of this, but really:
There is still a lot of uncertainty about omicron’s characteristics, especially its severity.
Yes, there are more and more pieces of the puzzle, but they don’t fit together all that well and there are a LOT of questions and hypotheses.
You can look at the current data and come up with a lot of theories - and the less you know the easier it is for that theory to fit what you know.
But some of the smartest people I know have told me they are simply not sure what to think yet.
Just one example:
I talked to @trvrb briefly yesterday (for a story to come later) and asked about data from South Africa on severity vs. early reports in Europe. He said: “I don’t know how to square these two things and that is probably giving me the most pause at the moment.”
Read 11 tweets
19 Dec
Germany’s new expert council weighs in on #omicron:

"Due to the simultaneous, extreme number of patients, a considerable overload of the hospitals is to be expected - even in the unlikely case of significantly weakened disease severity compared to the Delta variant"
They call for:
- further measures to reduce contacts
- enforcing current measures
- intensifying vaccination and booster campaigns
"all models show that booster vaccinations alone do not adequately contain the omicron wave, but that additional contact restrictions are necessary"
Beyond political decisions, "the population must be called upon to actively control infections. This includes avoiding larger gatherings, the consistent, preferred wearing of FFP2 masks, especially indoors, as well as the increased use of rapid tests at gatherings…"
Read 9 tweets
17 Dec
Going by what we know so far, places like Germany or the US are in for a world of trouble in the coming weeks.

So I want to make a few general points here once that go beyond the science (will do the rest later):
Firstly, why are we in trouble?
Forget everything else for a moment and just look at the growth rate of #omicron in places like Denmark and Norway. Look at London. This virus is moving fast. It spreads fast. And it will find those most vulnerable fast.
Unfortunately, places like Germany and the US still have a lot of vulnerable people who are unvaccinated.
This variant will find those people fast and if it is anything like previous variants it will make a significant portion of these people very, very sick.
Read 18 tweets
16 Dec
As promised, a brief thread on main points from the Denmark paper in @Eurosurveillanc looking at the first 785 cases of #omicron in the country.

Paper is here:
eurosurveillance.org/content/10.280…
@Eurosurveillanc First off: Things are moving incredibly fast with #omicron.
This timeline gives a good overview of how fast things happened in Denmark:
eurosurveillance.org/content/table/…
@Eurosurveillanc One key finding: More than one in five cases cannot be linked to previous cases.
"This indicates that within 1.5 weeks from identifying the first case of #Omicron, there is already widespread community transmission in Denmark, which challenges further epidemic control."
Read 9 tweets

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