Yesterday SAGE released a one-page document called "potential trajectories for covid-19 in the next six months"
It's not going to brighten your day, but it's one of the best summaries of where we are and where we're heading
Some notes 🧵
1. The “first” and “second” waves are very different
The second is growing much slower because of the impact of social distancing. Before this lockdown, contact rates were about half of pre-lockdown levels
But that's still not low enough.
2. Social distancing needs to be very extensive
SAGE: “With a basic reproduction number of 3, controls need to reduce infectious contacts by two thirds”
For a rough sense of what they means in practice, here's a chart of movement in London. It's been above 33% since June
3 – If we're not meeting people, immunity CAN play a role
SAGE: “When R is 1.1, only 9% of the remaining susceptible (i.e. not previously infected) population need to be infected for R to fall to 1”
(According to the most recent official figures, R is about 1.1 now)
4. BUT this isn’t the same as herd immunity. It only has an effect *because* of social distancing
Imho, this could help explain what’s happened in London. Movement has been lower there than in other cities so immunity could be playing a role at the margins
5. Without true herd immunity, there’s v. limited space to relax social distancing
If R is 1.1 and immunity reduces it to 1, SAGE reckons that "changes in effective contacts will be responsible for over 90% of control and immunity for less than 10%”
6. Relaxing measures will push R above 1 again very quickly, and cases won’t just go away
SAGE: The “natural” path of the epidemic is “a prolonged period of high incidence, with associated pressures on health services and deaths"
SAGE illustrates this with a graph of deaths in Florida. What they're saying is: even though the peak has come down, without intervention deaths will likely remain at this fairly constant level for some time to come :(
Maybe this all feels very obvious. In a way, it is. But the conversation around immunity has become so... strained... it's hard to see its proper role. It has one, it's just relatively small compared to social distancing - and it's likely to stay that way for some time / END
Unrelated, except in the sense of thinking about trajectories: this looks great
Incredible story in The Times, which I'm told is definitely true. For most of its existence, the contact tracing app for England and Wales has been using the wrong risk threshold, so it's hardly been sending out any alerts telling people to self-isolate thetimes.co.uk/article/softwa…
One of the biggest complaints about the app has been ghost messages saying "you've been near someone with covid-19". If the risk threshold hadn't been artificially high, many of those alerts would have been instructions to isolate
As it was, people were told to ignore them
The Times has described this as a software bungle. I understand the issue was incredibly human. There was meant to be a change to the risk threshold on the app, but no-one went in and made the update
Today, every media outlet carries shots of young people partying in Nottingham before Tier 3 came into force
In reality, confirmed cases in the city have been falling since early October, including among the young
This may well be because testing isn't picking up infections - and it seems as if cases in Nottinghamshire are rising among older people, which is a real concern
But the picture from pillars 1 and 2 doesn't seem to bear out the idea that young people are flouting restrictions
A graph to illustrate that point, using a fantastic app from @VictimOfMaths (ht @Telstar22995931). A huge spike among 15-to-24-year-olds (okay, students) which flattened off several weeks ago
Test and Trace is a strange, ephemeral organisation. The staff are largely consultants. The bosses are execs on secondment
If you're working there - or indeed any part of government - I'd love to know what you make of it. What's the rationale? How did it come to be that way?
The response to our story from DHSC emphasises the immense scale of T&T, which should never be underestimated. But the most common complain I hear about it is the lack of coordination. Wouldn't a permanent leadership team help with that? I'd genuinely like to know
Yes it's a hellsite, but here's why I love Twitter. Someone I've never met gets in touch to say his son has tested positive, but even though his whole family has the app, none of them have got a proximity warning. Twenty minutes later we're conducting a joint experiment
We're giving it half an hour. I'll let you know how it goes
It's now been 40 minutes and there's no alert. BUT... I forgot that the notifications aren't instant. They're sent out two-hourly to phones
Sorry if you were waiting for the result. It will be along as soon as I get it
MPs in the north of England are being told that pubs and bars are driving outbreaks. Mass closures are expected in parts of the country. Isn't this the the venue check-in system on the app is for?