21 Nov, 5 tweets, 1 min read
Query for immunologists...we need about 70% of the pop. to be vaccinated for herd immunity; ie. at 70% we get R=1. So lets call it 3.5m vaccinations. Can we do 500k/month? So this takes 7 months to achieve? What’s the effect of increasing vaccination levels by 500k/mth on R? 1/
In Jan we will be facing the prospect of a further lockdown as cases will be rising fast. If we start vaccinations in Jan then how will this help the R number. If 70% vaccinations imply R~1, then is there a linear relationship between vaccination level and R? 2\
Eg. in early Oct the national R number was about 1.2. If this is our baseline “being careful” rate, and if 10% of the population get vaccinated then does this reduce this baseline rate? By 10% ish? If so will R fall by 10%/mth due to vaccinations, all other things being equal. 3\
Haven’t checked the maths. Probably not that simple — behaviours may change — but presumably there is pressure on R as vaccinations proceed. Is it enough to avoid L5 in Jan. Maybe if vaccinations proceed & if we manage to limit the Xmas spike to create some breathing room. 4\
So, a plan: keep L5 as long as poss (Dec 14?); EU approves vaccine mid-Dec, rollout Jan; extra careful for Xmas to keep cases low as poss for Jan; vacs start in Jan w/ L3+ restrictions (economy open/no home visitors); as vacs increases restrictions relax w/ cases thru to July.

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# More from @barrysmyth

21 Nov
Some people have been asking about the ‘models’ I used in this graph to make case predictions beyond today. It’s very simple. There isn’t a model, at least not in the complicated way you might think. Wtf?!? Let me explain.
1\
Instead of using a complex predictive model & having a debate about parameters etc. I just used the case trend/numbers from waves 1 (red) & 2 (blue) after aligning the relative case numbers based on their peaks, as shown. Both waves are similar so this makes sense. 2\
Next, I ‘predict’ the remaining cases in (wave 2) L5 by assuming the trend will match that during the same period in wave 1 (ie the red line between Nov 20 - Dec 4, since I aligned wave 1 from March-June with wave 2 today). This gives the dashed blue line from Nov 20 to Dec 4. 3\
20 Nov
Level 5 seems well & truly stuck now, & each day brings a new even higher cases/day ‘prediction’ for an early Dec exit; its now 257 today, up from 223 yesterday. The problem is not only that cases are stalled/rising, but we have less and less time left to fix it before Xmas. 1/
That puts us >500c/d by Dec 25 & >900c/d by Dec 31, but that’s if transmission in Dec is similar to tx in Sept/Oct, which is surely very unlikely. Chances are, it will be markedly worse because of Xmas, so we’ll get more cases later in Dec & need a lockdown in early Jan. 2\
There are 19 counties on the naughty-list tonight (increasing transmission rates, week on week), up from 16 yesterday, including Dublin, and 6 of them now in the upper-right quadrant (high transmission & rising) which likely means further case increases in the coming days.
3 Nov
How are things going in Level 5? Cases and positivity rates are coming down nicely. How does this compare to wave 1 and can this help us to predict where we might get to by December? Let’s have a look ...
(1/n)
I’ve aligned waves 1 & 2 using their peaks. The y-axis is the 7d moving average of daily cases as a fraction of each wave’s peak. Wave 1 peaked at ~872 c/d and came down to about 50 c/d by June. So far, wave 2 has peaked at 1169 c/d & its falling. Where will it fall to?
(2/n)
Next, I (naively) extend wave 2 using the corresponding portion of wave 1; very simple yes, but probably a reasonable, if optimistic, estimate that saves on the modelling.

It suggests that we will get to about 144 cases/day on Dec 4.
(3/n)
2 Nov
Slovakia's drive to test its entire population over 2 weekends got off to a good start on Saturday with 2.5m tested and 1% positivity. Those 25k positives are now in quarantine. A voluntary programme with opt-outs required to quarantine for 10 days.
(1/n)
theguardian.com/world/2020/nov…
Next weekend the second half will be completed and presumably another ~25k positive cases will be found. So approx. 50k people will be in quarantine for 10-14 days. The remaining >5.4m people will presumably be free to go about their business with limited restrictions. (2/n)
There will be false positives among the 50k positives, possibly a fair few of them, but the alternative is that everyone goes into lockdown so this seems like a reasonable trade-off. There will also be false negatives circulating but there shouldn't be too many of them. (3/n)
1 Nov
This seems like an interesting experiment. Slovakia is testing entire population (5m) over 2 w/ends. Testing is ‘voluntary’ but those not participating must self-isolate for 10d. The first round covered 1m people with 1% positivity.
(1/n) @dwnews
In theory, absent issues with false negatives, could an approach like this drive the virus out of a country within a couple of weeks after testing? Imperfect because of false negatives and secondary tx during isolation, but it would surely do more than 6 was in L5 (for all) (2/n)
Eg, assume 1% positive rate from round 1 is correct, then Slovakia will end up with 50k people in isolation for 10-14days after a full testing cycle. After that cases will be the false negatives & secondary tx during isolation. (3/n)
1 Nov
We can now see transmission rates after L3, as we began L5. Much better than start of L3. Almost all counties either in or near the lower-left quadrant (low transmission & falling). A great good from which L5 can do its work if we all do out bit.