Brief thread to debunk the repeated claims we hear about transmission not happening 'within school walls', infection in school children being 'a reflection of infection from the community', and 'primary school children less likely to get infected and contribute to transmission'.
I've heard a lot of scientists claim these three - including most recently the chief advisor to the CDC, where the claim that most transmission doesn't happen within the walls of schools. There is strong evidence to rebut this claim. Let's look at this.

Let's look at the trends of infection in different age groups in England first- as reported by the ONS. Being a random survey of infection in the community, this doesn't suffer from the biases of symptom-based testing, particularly important in children who are often asymptomatic
A few things to note:
1. The infection rates among primary & secondary school children closely follow school openings, closures & levels of attendance. E.g. We see a dip in infections following Oct half-term, followed by a rise after school reopening.
We see steep drops in both primary & secondary school groups after end of term (18th December), but these drops plateau out in primary school children, where attendance has been >20% after re-opening in January (by contrast with 2ndary schools where this is ~5%).
Concerningly, the REACT-1 study data released today show that prevalence of infection across England is now highest in primary school children & young adults, with the drops being less steep in primary school children compared to other age groups.
These data are consistent with outbreak data from PHE surveillance, showing that outbreaks in primary schools & pre-school settings continue to occur (albeit at a lower rate than before in primaries), but much more than in secondary schools- in line with higher attendance.
This evidence also feeds into the second myth we hear about - that primary school children don't contribute substantively to transmission. This simply doesn't hold up to scrutiny. The plot from the PHE shows that the number of clusters of cases has been very similar in both.
We also see from the ONS data that primary and secondary school children had the highest prevalence of infection in the community compared to all age groups in December, prior to school closures -prevalence was 2% among primary school children and 3% in 2ndary school children.
All this evidence strongly suggests that infection among children is not simply 'a reflection of infection in the community'. It makes no sense to think that children are getting infected in their households and not within schools.
It's clear that infection in children closely tracks school openings, closure, & the level of attendance. We've seen this in England time and time again. And it's not just secondary schools. It's clear that primary schools play an important role. What about global evidence?
This comprehensive study in Nature Human Behaviour that looked at thousands of interventions implemented at different time points in >200 countries showed that closure of educational institutions was one of the most effective interventions in reducing R.
nature.com/articles/s4156…
But what about the impact of closure of preschool vs primary vs secondary schools. There was no difference- all of them were similarly effective in reducing R- and closure of any setting had a substantial impact on reducing R.
We also have evidence from the UK from our last lockdown in November, when schools were open, and regions where the new variant was dominant (as it is across the UK now) were showing increases in cases (R>1). R in these regions dropped to below 1 only after schools were closed.
This real-world evidence is reflected in recent modelling by LSHTM that also suggests that in almost all scenarios opening primary or secondary schools would lead to rises of R above 1 in England.
It's astonishing that despite all this evidence, the need for mitigatory measures in schools in England has been ignored, and we still promote the myth that primary school settings don't contribute significantly to transmission, and that transmission doesn't happen within schools
We don't have to even look to the 8th of March when the govt is planning to reopen schools. We're having outbreaks in schools now - in preschool & primary school settings. Primary school children have the highest prevalence of infection along with young adults. When will we act?
Want to end on the ONS data on school transmission from last year that showed that primary school children were 2x more likely than adults to be the first case in the household, and once infected, 2x more likely to infect contacts than adults.

This is some of the least biased evidence we have - as it's based on random surveys of children so not dependent on them being symptomatic, and tested. Why are we ignoring this breadth of evidence to the detriment of children, teachers, and communities?

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More from @dgurdasani1

16 Feb
Modelling preprint from LSHTM published showing that in almost all scenarios, opening schools at this point in England without additional mitigation results in R rising above 1, and exponential rises in cases resuming. Short thread
First, these results are unsurprising given that in our last lockdown in November, new variant cases were rising with an R of 1.45 even during lockdown, but while schools were open. This is the best comparator given the new variant is now dominant across England.
In almost all scenarios R rises above 1 (we are at ~0.8 or so now) when opening primary or secondary schools or both.
Read 6 tweets
14 Feb
Just an observation that while we're still debating mask use in schools in the UK, countries in Europe are revising policy on grade of masks in school (e.g. France on surgical or FFP2 grade masks in schools). Exceptionalism means we're constantly behind on evidence-driven policy.
In the UK, we've built ideologies around exceptionalism.

'Our children wouldn't tolerate masks' (despite millions of children around the world & in Europe wearing these - both in primary & secondary school settings - without any evidence of harm).
We live in an environment where we feel children are exceptional in that they aren't very susceptible to infection, or don't transmit much, and school environments are exceptional environments where significant transmission doesn't occur. These ideas are not grounded in evidence.
Read 5 tweets
13 Feb
Am going to talk about my experience with media bias around discussions of zero COVID & how this is shaping our COVID strategy. I've encountered this again & again. Am also going to speak about why it's important we consider elimination from an evidence based perspective. Thread.
Yesterday I was contacted by a prominent BBC programme to speak about strategy for exit from lockdown & the role of scientists & politicians in defining this. I outlined elimination as a preferred strategy and provided factual arguments to support this on being challenged.
I was told this was 'interesting', but later told me the programme had moved in a different direction (not on zero covid). This has happened to me before. I watched the show- it was clear that the same issues were discussed *except* elimination was not considered at all.
Read 37 tweets
12 Feb
This is irresponsible & negligent- we haven't learned anything from past mistakes. Letting a big wave of infection flow through the UK would mean hundreds of thousands of people with long COVID, and further virus adaptation & spread that may threaten vaccine effectiveness.
We can't count on being able to tweak vaccines to keep on top of virus adaptation- adaptation has happened much faster than we imagined- and is continuing in a way we can't predict. This is the same as the 'focused protection' & herd immunity strategy promoted by the GBD.
We've literally seen the impact of this strategy- which has given rise to more transmissible variants, and more recently variants with mutations that can potentially reduce vaccine effectiveness. We have exported these variants to much of Europe, with impact for pandemic response
Read 4 tweets
12 Feb
Worrying data from the most recent PHE surveillance yesterday - despite these data really underestimating infection in children (as they are based on symptom based testing), positivity rates appear highest in early year settings (fully open) & primary schools (20% attendanc).
The real differences are likely to be greater, given that much of infection is asymptomatic in children. Also worth noting the steep drop initially after school closure, which then plateaus to become more gradual after school re-openings.
Infection among children closely tracks school openings and closures (as we saw even during october half term), and level of attendance (trends in secondary schools where attendance is much lower are different). Again in line with substantial transmission occurring in schools.
Read 4 tweets
11 Feb
“If we let variants emerge, amid high transmission rates, that new variant could easily overtake the whole viral population,” @GuptaR_lab

Stark contrast to the rhetoric from JVT at the briefing earlier this week. We need to contain transmission urgently

theguardian.com/society/2021/f…
Let's remember that E484K has emerged on the background of the UK variant, not once, but many different times- this means that the virus is evolving in this direction. And if it's allowed to continue adapting, through high levels of transmission, it will continue to do so.
And as I've said before, as pressure from vaccine-acquired immunity mounts, we should expect the selection pressures on the virus to be different - it's entirely possible that if high transmission is allowed to continue alongside vaccination, this will create pressure for escape.
Read 5 tweets

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