🧵
A couple of things people I think people have misunderstood about the school DCT study - lets clarify them!

First, test sensitivity of "only 53%"

Does this mean the test is rubbish?

Well actually, it's irrelevant!

1/
There is a BIG difference between a study of test performance, and real world test implementation

Good tests can be harmful in the real world, bad tests can end up being useful

For this study, we don't care about performance...

2/
This study measured secondary cases compared to quarantine - the outcome we actually care about is people getting infected

There is no noticeable difference here. It could be both are equally terrible! the important thing is there is not a big difference

3/
Next, concerns about the non-inferiority level are overblown, because they ignore that this is relative, not absolute

Rates of secondary cases were <2%. A 50% increase from e.g. 1.5 to 2.2% is negligible in real terms, and would be well worth not dismissing bubbles

4/
People draw attention to relative risks like this to obscure the true impact of the intervention

Besides, the result was well within this margin - the upper CI was 1.22, so a max 22% increase (e.g. 1.5% to 1.83%, or 2% to 2.44%) - tiny real increase

5/
This shouldn't be impacted by community transmission either, as this is rates per index case. More spread elsewhere will just mean more index cases.

There you have it - don't let statistical wizardry or misdirection pull the wool over your eyes!

6/

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More from @apsmunro

23 Jul
🧵
Are trials of daily contact testing vs quarantining in schools "unethical"

tldr:
No. They never were, and are obviously not only ethical, but desirable, now we have results of a study

1/
A main concern was regarding equipoise - meaning, was there a balance before a trial of which would be better?

There absolutely was, including in modelling from spi-m, and I outlined that thinking previously here

2/
Results of the study show that there is likely little difference between the two, and testing results in less absence

If there is a difference (there is a range of uncertainty), it is very small, and unlikely important

Obviously there was not a huge difference = equipoise

3/
Read 6 tweets
23 Jul
This is BRILLIANT news!

A randomised trial of daily testing of school contacts of COVID-19 cases found it was just as good (or maybe better) at preventing transmission than sending kids home

It kept kids safe AND in school

This is why we do research ❤️

bbc.co.uk/news/health-57…
There is so much to talk about with this study I will be banging on about it all day

Massive congratulations to the team who put this together

This is evidence which can inform policy all over the world - so proud of the UK leading the way on evidence based policy here
Just in case you come across any strange claims of the study being unethical...

Read 4 tweets
13 Jul
Some seems to be some confusion on why it's better to coincide easing of restrictions with schools closing for summer

If schools are not drivers of community transmission, why does it matter?

Don't worry, it's quite simple! Let me explain...

1/
Firstly, closing schools does not just stop transmission in school

When schools are closed, adults have to stay home, change their plans etc to look after children

This appears to be a pretty major source of reduction in R associated with school closures in general

2/
For example, modelling frequently shows closing Primary schools to reduce R by a greater degree than closing Secondary schools, despite more transmission occurring in Secondary age children

This is likely because closing primary schools forces more parents to remain home

3/
Read 8 tweets
12 Jul
It's important we are all cognisant of the impact of highly emotive and fear based messaging around #COVID19

It can create deep and lasting damage, and is often counter productive

This is especially the case when it comes to children

1/
It is great to use facts to and establish risk and to inform people (although for kids this is almost universally reassuring when used in the right context)

But to deliberately stoke fear and anger is not healthy, and will not end well

None of this is new to public health

2/
There is a long history here with HIV in particular

Potentially creating lasting fear and stigma around sexual relationships

Are we creating the same around social experiences? Around our children attending school?

How are we communicating?

3/

journals.sagepub.com/doi/10.1037/10…
Read 8 tweets
10 Jul
Already people are misunderstanding the new paper showing extremely low risk of children from #COVID19

The paper reports both the population risk to children, AND the infection risk

It also massively *overestimates* the infection risk to children

1/
researchsquare.com/article/rs-689…
The study uses PHE modelling data on infection rates, as case data over the year is unreliable (we tested only people who were admitted to hospital during the first wave)

Through this, they estimate just short of 500,000 infections

This is a massive underestimate

2/
We can get a better estimate of total infections by measuring seroprevalence - who has positive antibodies

By July last year, 4% of children were positive - that is already nearly 500,000 BEFORE the second wave

3/
assets.publishing.service.gov.uk/government/upl…
Read 5 tweets
1 Jul
A quick 🧵on testing kids for #SARSCoV2

Many people believe children are more likely to have false negative results to:
- antibodies tests, due to them having mild illness
- PCR tests, due to difficulty sampling

Turns out, that's almost never the case

1/
First, antibody tests

Most serology tests used in studies test for antibodies against the Spike protein (we call these S IgG)

This nice Australian study, found no difference in rates of children seroconverting to S IgG compared to adults

2/
wwwnc.cdc.gov/eid/article/27…
In fact, not only that - but this study shows younger children actually have HIGHER S IgG levels than adults!

Their super immune systems make a bangin' response

Good work kiddos

3/
sciencedirect.com/science/articl…
Read 9 tweets

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