Thus, it looks clear to me that most places in America are going to make it given the additional vaccinations that will take place, but some places with low vaccination rates will fall short.
I found myself intuitively skeptical about this claim and tried evaluating it via a different line of reasoning than the one you used (but relying on some of your figures). After going through this, I mostly updated that it will be a close race with the vaccinations. Overall, I find it 65% likely that places with a roughly average vaccination coverage in the US won’t be able to avoid large surges in case numbers (defined by either lockdowns or really strong new restrictions, or 3% of unvaccinated people infected at the same time.) (This could be compatible with your estimates, because the death rate in well-vaccinated areas would still be relatively low if vaccination uptake is high amongst the elderly.) What seems very clear is that locations with below-average vaccination coverage will be in trouble.
My approach and estimates:
I think a crude lower bound for when you get Delta variant under control is when you have a substantially larger percentage of the population vaccinated than the UK currently has. (Because R is 1.1-1.35 in the UK now and that’s before the full reopening.)
Current vaccination percentages for the UK (all age groups): 63.3% first dose 46.0% second dose
Current vaccination percentages for the US (all age groups, I think): 52.7% first dose 44.1% second dose
You say there’s about 25% Delta variant in the US now.
5 weeks ago, I commented that the UK had >50% Delta variant in some areas. With a doubling time of roughly 11 days in the UK, it must have been at 25% roughly 7 weeks ago. Meaning, assuming that the infection levels in the US currently are comparable to what they were in the UK 7 weeks ago, then the US is roughly 7 weeks behind the UK timeline.
7 weeks ago, the UK was reporting around 2k Covid cases (with a population of 66 million). The US population is 5x larger. The US is presently reporting around 13k cases. That’s similar enough! Therefore, I’m going to operate under the assumption that the US is “7 weeks behind the UK timeline.”
The situation in the UK is concerning and getting worse still, but the case numbers are substantially below the previous peaks. I’d say the UK is about 3-4 weeks ahead of things getting very bad.
By that reasoning, the US has roughly 10 weeks to get R below 1 for the Delta variant.
You say, “Currently [the US] are vaccinating about 1% of people each week.”
I’m assuming that’s both doses?
Continuing with that, in 10 weeks, the US should have the following vaccination percentage:
62.7% first dose 54.1% second dose
And here the present UK numbers again:
63.3% first dose 46.0% second dose
The UK is not fully reopened yet, and R is at 1.1-1.35. Most UK experts are pessimistic about things getting better anytime soon, despite vaccinations progressing quite quickly.
That said, the second dose may matters more than the first dose, especially if the first dose is Astra Zeneca. So, 54% second dose instead of 46% should make quite a large difference. I think (?) the US also relies slightly more on Pfizer and Moderna than the UK, which should add a bit of extra protection. Summer temperatures also help out. But is all of this enough to put R below 1 (for the Delta variant, specifically) early enough?
The UK isn’t even fully opened yet. Some US states may go ahead with the full reopening now, in which case they’ll have less than the projected 10 weeks until they catch up with the UK timeline.
Then again, there’s room for the vaccinations to speed up (the vaccination rate used to be higher at points in the past).
Note that my definition of “large surges in case numbers” isn’t necessarily that bad. 3% of unvaccinated people infected – the UK is almost there already, and deaths are extremely low because the unvaccinated people are mostly really young.
Update: I’m realizing that country-wide infection counts are driven mostly by the places with the worst vaccination uptake, so a location with an average vaccination rate wouldn’t be hit that badly compared to the country average infection rate. This means I’d now change my operationalization to something like “worst 25th percentile.” And maybe make it 60% instead of 65%.
I mentioned it as a consideration, but yeah, I’m probably underestimating the effect of that by a lot, now that I think about it. I wasn’t sure how much the US has so far relied on the J&J vaccine, which is also less effective. But it looks like it’s a low amount of it.
Regarding the estimate that Delta is 40% more infectious than Alpha: I’ve seen 50-60% mentioned a lot in the last couple of days from UK expert sources. If true, this would probably make a big difference to your calculations.
Ah, I used 40% first, then used 60% in the later calculations as I gathered more data, and forgot to go back and update. But I used 60% (57% or so actually, but close enough) in my base calculation.
I found myself intuitively skeptical about this claim and tried evaluating it via a different line of reasoning than the one you used (but relying on some of your figures). After going through this, I mostly updated that it will be a close race with the vaccinations. Overall, I find it 65% likely that places with a roughly average vaccination coverage in the US won’t be able to avoid large surges in case numbers (defined by either lockdowns or really strong new restrictions, or 3% of unvaccinated people infected at the same time.) (This could be compatible with your estimates, because the death rate in well-vaccinated areas would still be relatively low if vaccination uptake is high amongst the elderly.) What seems very clear is that locations with below-average vaccination coverage will be in trouble.
My approach and estimates:
I think a crude lower bound for when you get Delta variant under control is when you have a substantially larger percentage of the population vaccinated than the UK currently has. (Because R is 1.1-1.35 in the UK now and that’s before the full reopening.)
Current vaccination percentages for the UK (all age groups):
63.3% first dose
46.0% second dose
Current vaccination percentages for the US (all age groups, I think):
52.7% first dose
44.1% second dose
You say there’s about 25% Delta variant in the US now.
5 weeks ago, I commented that the UK had >50% Delta variant in some areas. With a doubling time of roughly 11 days in the UK, it must have been at 25% roughly 7 weeks ago. Meaning, assuming that the infection levels in the US currently are comparable to what they were in the UK 7 weeks ago, then the US is roughly 7 weeks behind the UK timeline.
7 weeks ago, the UK was reporting around 2k Covid cases (with a population of 66 million). The US population is 5x larger. The US is presently reporting around 13k cases. That’s similar enough! Therefore, I’m going to operate under the assumption that the US is “7 weeks behind the UK timeline.”
The situation in the UK is concerning and getting worse still, but the case numbers are substantially below the previous peaks. I’d say the UK is about 3-4 weeks ahead of things getting very bad.
By that reasoning, the US has roughly 10 weeks to get R below 1 for the Delta variant.
You say, “Currently [the US] are vaccinating about 1% of people each week.”
I’m assuming that’s both doses?
Continuing with that, in 10 weeks, the US should have the following vaccination percentage:
62.7% first dose
54.1% second dose
And here the present UK numbers again:
63.3% first dose
46.0% second dose
The UK is not fully reopened yet, and R is at 1.1-1.35. Most UK experts are pessimistic about things getting better anytime soon, despite vaccinations progressing quite quickly.
That said, the second dose may matters more than the first dose, especially if the first dose is Astra Zeneca. So, 54% second dose instead of 46% should make quite a large difference. I think (?) the US also relies slightly more on Pfizer and Moderna than the UK, which should add a bit of extra protection. Summer temperatures also help out. But is all of this enough to put R below 1 (for the Delta variant, specifically) early enough?
The UK isn’t even fully opened yet. Some US states may go ahead with the full reopening now, in which case they’ll have less than the projected 10 weeks until they catch up with the UK timeline.
Then again, there’s room for the vaccinations to speed up (the vaccination rate used to be higher at points in the past).
Note that my definition of “large surges in case numbers” isn’t necessarily that bad. 3% of unvaccinated people infected – the UK is almost there already, and deaths are extremely low because the unvaccinated people are mostly really young.
Update: I’m realizing that country-wide infection counts are driven mostly by the places with the worst vaccination uptake, so a location with an average vaccination rate wouldn’t be hit that badly compared to the country average infection rate. This means I’d now change my operationalization to something like “worst 25th percentile.” And maybe make it 60% instead of 65%.
I think you’re not factoring in that a lot of UK vaccinations are AZ, which is a lot less effective at stopping spread?
I mentioned it as a consideration, but yeah, I’m probably underestimating the effect of that by a lot, now that I think about it. I wasn’t sure how much the US has so far relied on the J&J vaccine, which is also less effective. But it looks like it’s a low amount of it.
Regarding the estimate that Delta is 40% more infectious than Alpha: I’ve seen 50-60% mentioned a lot in the last couple of days from UK expert sources. If true, this would probably make a big difference to your calculations.
Ah, I used 40% first, then used 60% in the later calculations as I gathered more data, and forgot to go back and update. But I used 60% (57% or so actually, but close enough) in my base calculation.
I’ve edited to reflect this.