Here's another way of looking at the incredible effectiveness of COVID vaccines against mortality.
As successive age groups began to be vaccinated, the % of cases in that age group which led to a death (the Case Fatality Rate) started to fall sharply.
Note the log scale on the y-axis (thanks @ikashnitsky) to ensure that each halving of the CFR takes up the same vertical distance.
The pattern is basically unchanged if you put it on a linear scale in case you were wondering.
Maybe if you are of a cynical bent you might think 'Ah, but Colin, if the CFRs have just been falling consistently over time, you'd see this pattern even if the vaccines didn't work'. But they haven't, as we can see if we extend the y-axis back in time.
The recent 'wobbliness' in these trends across all age groups is likely to be the initial effect of the Delta variant, which appears to have worse outcomes for each case, so is likely to push the CFR up a bit. We'll have to wait and see exactly how far.
Huge credit to Daniel Howdon for doing the hard work to estimate the Case Fatality Rates.
R code for the plots (although without the CFRs themselves as they are not mine to share, sorry) is here: github.com/VictimOfMaths/…
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A conversation with @jburnmurdoch yesterday sparked an idea for a new plot to try and illustrate how different we'd expect the number of deaths due to the current COVID outbreak in Bolton to be compared to previous waves.
A lot going on here, so let's unpick it a bit...
Clever people like Dan Howden (formerly of this parish) have been using published data on COVID cases and deaths by age to estimate age-specific Case Fatality Rates - the % of cases in an age group which leads to a death within 28 days. cebm.net/covid-19/the-d…
For any day's newly announced cases, we can use these numbers to estimate how many deaths we'd expect to result from those cases, accounting for the age profile of cases.
Thinking about this a bit more, it seems very plausible that 1 won't happen (much*) and 2 and 3 will.
This would lead to a scenario where there are widespread infections across the country, but overwhelmingly in unvaccinated, younger, lower risk groups...
This would lead to a small rise in hospital admissions (as we're already starting to see in the NW) and deaths (relative to what has gone before), and potentially a bigger rise in other consequences like long COVID, although the evidence around that is much more uncertain (AIUI).
Which raises the question of how government would respond. They could either take action to try and limit the spread (be that local restrictions or national lockdowns), or they could just let the virus spread as the consequences will be far less severe than uncontrolled spread...
I remembered that NHS England publish daily admissions data at regional level, so here's what those numbers look like.
Admissions have started to rise in the Midlands and North of England, and bed occupancy and ventilator use have risen in the NW. But the numbers are small.
What happens next depends on three things (I think):
1) Do cases in areas with high case rates just now spread into older age groups 2) Do vaccines lead to fewer admissions and deaths even if cases do spread to older age groups
3)Do cases start to rise widely elsewhere
I'm not going to make predictions, but I'm still not too pessimistic.
Scotland don't publish an age breakdown of COVID cases at Local Authority level (I don't think), but the national picture shows the same pattern as we see in parts of England where cases are rising - cases are only increasing in the under 45s.
This is a different pattern from both October (cases started in teenagers then moved up the ages) and January (cases rose in all age groups at once).
Vaccines, innit 💉💪
Here's a bonus streamgraph version, for those of you who like that sort of thing.
Because the profile of cases is much younger than previous waves, the expected mortality rate is much lower.
If there were no more cases, we'd expect 4 deaths over the next month or so.
Obviously 4 deaths is 4 more than we'd really like, but compared to the 738 deaths to date in Bolton, it's clear that this outbreak is (at the moment) nothing like what has come before.
Even over the whole of the North West the number of cases we've seen so far are expected to lead to just 24 further deaths.