As we are beginning to get some useful data on the current VOC this may be a good time to review what we know.
Case counts are rocketing (nearly 3 times any previous wave), and showing no signs of slowing, as the graph below shows.

There is some, very tentative, evidence that it may be less clinically severe but it is doubtful that this will be enough to stop a flood of hospitalisation and probably deaths. Even if the hoped for drop in virulence significantly reduces the severity, on a case by case basis, the far higher case loads will negate that advantage. Looking at the graph there has not been enough time between the start of the current exponential case growth (the last 3 weeks) to see how that plays out in terms of the deaths due to the lag time of about two weeks for hospitalisations and a month for fatalities.
Omicron definitely has a significant fitness advantage over the other variants but it is very hard to compare with Alpha and Delta, which also rapidly established themselves, as the population's immune profiles have changed so much.
The graph below shows how quickly Alpha (red), Delta (greens) and Omicron (purple) established themselves and then got supplanted. I have used the UK data as they do the most case sequencing and are well globally connected.

What data there is comes from early case data in South Africa which shows lower, or at least slower, hospitalisations than delta and very different demographic profiles. The age, sex, comorbidities and O2 need are all very different. (compare column 4 to the earlier VOCs. N.B. also that this is a smaller data set so the confidence limits will be larger).

The next bit of useful data comes from https://www.medrxiv.org/content/10.1....27.21268278v1 which basically shows that at least part of Omicron's fitness advantage comes from immune evasion but a booster vaccine dose helps reduce this. It, along with other data, shows Omicron has a shorter incubation period.
There is also good evidence that Omicron cause less sever symptoms in mice and hamster models with less replication in the lung but high replication in the nose. As usually with animal models it is difficult to say if this has any relevance in humans.
My guess would be that it is a bit milder but very fit. This is good if it reduces morbidity but probably also bad if it leaves more mild and asymptomatic cases shedding and accounting for its explosive growth. I would be very cautious for a while in your contacts with others - distance, wear a mask and, if you can, get vaccinated and boosted. I think our health care services are going to have a hard time coping over the next few months and will need all of us to reduce our risk as much as we can.
The top graph is from the current WHO sitrep
https://www.who.int/docs/default-sou...&download=true
The variants tables can be found here
The SA data
https://jamanetwork.com/journals/jam...rticle/2787776
The mouse/hamster data
Case counts are rocketing (nearly 3 times any previous wave), and showing no signs of slowing, as the graph below shows.
There is some, very tentative, evidence that it may be less clinically severe but it is doubtful that this will be enough to stop a flood of hospitalisation and probably deaths. Even if the hoped for drop in virulence significantly reduces the severity, on a case by case basis, the far higher case loads will negate that advantage. Looking at the graph there has not been enough time between the start of the current exponential case growth (the last 3 weeks) to see how that plays out in terms of the deaths due to the lag time of about two weeks for hospitalisations and a month for fatalities.
Omicron definitely has a significant fitness advantage over the other variants but it is very hard to compare with Alpha and Delta, which also rapidly established themselves, as the population's immune profiles have changed so much.
The graph below shows how quickly Alpha (red), Delta (greens) and Omicron (purple) established themselves and then got supplanted. I have used the UK data as they do the most case sequencing and are well globally connected.
What data there is comes from early case data in South Africa which shows lower, or at least slower, hospitalisations than delta and very different demographic profiles. The age, sex, comorbidities and O2 need are all very different. (compare column 4 to the earlier VOCs. N.B. also that this is a smaller data set so the confidence limits will be larger).
The next bit of useful data comes from https://www.medrxiv.org/content/10.1....27.21268278v1 which basically shows that at least part of Omicron's fitness advantage comes from immune evasion but a booster vaccine dose helps reduce this. It, along with other data, shows Omicron has a shorter incubation period.
There is also good evidence that Omicron cause less sever symptoms in mice and hamster models with less replication in the lung but high replication in the nose. As usually with animal models it is difficult to say if this has any relevance in humans.
My guess would be that it is a bit milder but very fit. This is good if it reduces morbidity but probably also bad if it leaves more mild and asymptomatic cases shedding and accounting for its explosive growth. I would be very cautious for a while in your contacts with others - distance, wear a mask and, if you can, get vaccinated and boosted. I think our health care services are going to have a hard time coping over the next few months and will need all of us to reduce our risk as much as we can.
The top graph is from the current WHO sitrep
https://www.who.int/docs/default-sou...&download=true
The variants tables can be found here
The SA data
https://jamanetwork.com/journals/jam...rticle/2787776
The mouse/hamster data
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