We're still mostly dealing with Delta at this point.
I'm hoping Omicron is more virulent but less deadly. That would be pretty big, because it would squeeze Delta out.
But the bad part is that Omicron is more resistant to vaccine, in terms of catching it -- still reduces, but not as much as the vaccine vs. the other variants. Vaccine + booster is doing very well as prevent serious illness though, still, which is ultimately what matters most.
And we're learning still. We don't have our own data yet -- I think we're relying on South Africa info, if I'm not mistaken.
There's absolutely no question Omicron is more virulent. How much is the question. The early reports that it was maybe milder were from South Africa where the age profile is completely different than in the West. The latest out of the UK is that there's no reason (yet) to believe it to be milder, but since disease severity data lags initial positive tests by several weeks, it's still very early.
If you want an indication of virulence, you can look at a place like Copenhagen in Denmark. They variant test every single positive PCR sample, so they can tell with very high precision exactly what the development is. On 27 Nov they detected the first 3 Omicron cases out of about 4000 total cases (less than 0.1%). A week later it was 1.5% of all cases. A week after that it was 15% of all cases. A week later (about now) it's 50%. Copenhagen has a heavily vaccinated population and since Omicron can infect the vaccinated to a much greater degree, it's not quite that simple to calculate the relative virulence (since Omicron effectively has a *much* larger pool of people to spread in), but it's clearly more virulent. Recent UK data indicates vaccine (2 doses) efficacy around 0-20%, with booster around 55%-80%, although that data might be affected by the time lapsed since vaccination (basically, most people in the UK had their second shot 6 months ago, so protection *now* is bad, but we don't know what it is for people who *just* got a second shot).
https://www.cidrap.umn.edu/news-perspective/2021/12/uncertainty-swirls-around-omicron-covid-19-severity
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