Omicron -scenarios and planning for worst case/best case

Photo by cottonbro on

I wanted to try and visualise the challenge facing decision makers over the next few days/weeks as the Government attempts to decide what to do about the Omicron variant if anything.

I thought the best way to do it might be to give you a simplified model. This isn’t as high powered as the types of models available to SAGE and Imperial College. Nor, given I’ve knocked this up in 15 minutes does it have all the data and assumptions you would need to do things properly but here goes.

I’ve provided three scenarios below. I’ve started with the current rolling average of cases. I’ve then for each one given a range of scenarios for hospital admissions ranging from 1.5% where Omicron is less severe in its impact through to 3% where it is much more.

Then I’ve considered the possibility that through Vaccine boosters taking effect, the natural cycle of an epidemic wave and a level of modified behaviour that we might either see cases continue to rise at a significant rate followed by a fall. My scenarios assume different levels of impact so that in the second case we see cases continue to rise significantly for a longer period whereas in the third case we see them beginning to drop quite quickly.

Let’s have a look:

Scenario 1
Scenario 2
Scenario 3

I’ve then assumed that as we saw admissions of around 4k plus per day at the previous peaks that it would be over this amount that we would find ourselves in serious trouble. I’ve then assumed that anything over 2k per day is likely to stretch the NHS and cause a significant level of concerns.

If I were part of the Government team making decisions I would look at the above scenarios. I would conclude that we don’t have to worry too much about the third scenario, providing admission rates stay at between 1.5 -2% but I would be more concerned about the first and second scenario. It is in those cases that we would need to take action.

Now, this is the crucial step that I haven’t heard people talking enough about, how we move from scenario to prediction. The crucial step here is probability or likelihood. So, if I were sat at the table with Boris Johnson and Sajid Javid, then I would be asking

  • What is the probability of admission rates increasing over 2%?
  • What is the probability of cases continuing to grow at over 50% for more than another week?

I would expect SAGE and other experts on the team to be able to help us answer that question based on what they are already seeing both here in the UK and from other countries. Added to that they’ll have modelled human behaviour and they should have plenty of lab and real world study data on things like vaccine efficacy and the virulence of the variant coming in by now.

For example, we have information suggesting that the booster jabs give something like 70-75% protection against infection and 93% protection against serious disease. We have data suggesting that the South African Omicron wave is peaking and we will hopefully be getting more data in from London where the Omicron wave appears to be ahead of the rest of England.

If we are already seeing the heat taken out of case growth rates on a sustained basis by Tuesday/Wednesday this week and admission rates remain around about 1.5% -2% especially in London then we can conclude that there is low probability of our worst case scenarios. We cannot rule them out completely but we can worry about them a little less.

If on the other hand, we are seeing a fresh surge in growth and/or admissions climbing as a percentage of cases then this will suggest a higher probability for worst case.

Personally, my gut feel is that the first scenario is probably the most likely in terms of case numbers and the third the least likely (this could be affected by wishful thinking and my passionate hope that we don’t see the second scenario play out). That’s why I still believe that everything comes down to the efficacy of the vaccines and the effectiveness of their role out.

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