UK’s Delta Experience Forshadows the US

I have been tracking how Delta has been moving through the UK lately. There were a few reasons.

  1. This was the first place with good genetic survellience (arugably, the UK is doing better than anyone else, They certainly were doing well with it first) So I could REALLY see if Delta was going to outcompete Alpha (aka the highly transmissible B.1.1.7 which was first noted in the UK and drove their December surge.)
  2. Delta got established in the UK earlier than anywhere but India, so I believe watching how it moves is a good model to see how Delta will move through somewhat vaccinated nations/areas, like the US.
  3. Ditto to 2, and toss in that England is industrialized with a robust (in normal times) health care infrastructure, like the US.

My conclusion is that even in a 50–60% vaccinated population, this thing spreads pretty dang quickly and quite steadily. That slope has not budged. This graph runs through July 5th. This weeks data is more of the same.

The good news is vaccinations help a lot with lowering hospital admissions. This plot shows they are about 50% what might have been expected with this case load, which, unsurprisingly is roughly the percentage of not fully vaccinated peeps in England. The 8 day lag I used for the orange line was based on the lag between peak hospitalizations and peak new cases in the UK in earlier pandemic phases . It takes some time after infection for people to get sick enough to need a hospital. How that 8 day guess is tuned changes things some, but not a lot.

Delta in the UK is the US’s future

My takeaway is there is basically no place in the US that will do much better than Britain: we have similar vaccination rates. The ONLY difference is Delta established itself in the UK earlier by about 3 weeks. A 2nd order difference is the US has a lower pop density, but from a populations perspective, the US is pretty urban and suburban. Still less dense than a lot of England so a small advantage.

With the varying vacination rates in different areas, we will see how different vacc rates impact that log slope. In Britain it is steep enough I will be shocked if the difference between 50% and 70% vaccinated changes the slope from upwards to downwards.

In other words, I expect Mighty Vermont with its 66% fully vaccinated rate (see to have problems with Delta if they socialize, continue to go maskless etc. Their slope will just be slower than the UK.

The Warning of Israel

Israel is another good analogue since its vaccination rate is a bit better than the US. Israel was a vaccination poster child getting out front of every one else and life has been more of less back to normal for a few months.

Now, look at how their raw cases have climbed the past few weeks. The green dots look like 7 day trailing average (I don’t read Hebrew) . The y axis seems to be total new cases, not per 100k people. Their numbers are still reasonably low (about 4.6 new cases per 100k), but high enough to be seriously concerning given the trend. They are up a factor of 30 in cases since mid June. Yikes.

It is also telling that with Israel’s early relatively high vaccination rate, their pandemic was really sort of over…until Delta established itself. The one good thing about Israel’s situation is the fast increase in cases seems to have driven a positive change in the completely plateaued slope of first doses (Scroll on up to their vaccination profile) starting in the last week of June. Maybe the US’s Delta moment will drive a similar result here.

SF Bay Area: An Emerging Hotspot

A final note on the San Francisco Bay Area. Our vaccination rate is higher than Israel’s. Going by county, some are even higher than Vermont. At the same time, people have pretty much ditched masks and are gathering indoors in bars and house parties, etc. When we look at what a difference Delta made an Israel I suspect the Bay Area will see problems . Given the number of breakthrough cases and the demonstrated ability of unvaccinated children to transmit it to adults, we will see climbs here too. They have already begun but the trend is still young.




I have a background in science. I back up nearly everything science I write with peer reviewed research, or at least preprints and pointers to my data sources

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David Theil

David Theil

I have a background in science. I back up nearly everything science I write with peer reviewed research, or at least preprints and pointers to my data sources

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