Thread by @apsmunro

"If there's one thing we learn from history, it's that we don't learn from history"

A new study from India looks at #COVID19 contact tracing

And now reported, "[children] transmitted the virus at rates similar to the rest of the population"

🤔

latimes.com/world-nation/s…

1/10

There is SO much to dig in to here because these findings are complex - but we'll stick with the major issues for now

Child index cases were found to have a high proportion of positive contact of the same age

They must infect them easily, right?

science.sciencemag.org/content/early/…

2/10

The first caveat, is that to be defined as a index case, the child was almost certainly symptomatic

Symptomatic people seem to be much more infectious than asymptomatic

A large proportion of children seem asymptomatic (~50%) so findings are not generalisable

But wait...

3/10

We've been here before

Remember this study from South Korea which was widely reported to show children aged 10 - 19 were just as infectious as adults?

wwwnc.cdc.gov/eid/article/26…

4/10

And remember this study ON THE SAME DATA which corrected for shared exposure (the index case and suspected secondary case both exposed to same original infection source) and found extraordinarily low rates of confirmed secondary infections?

adc.bmj.com/content/early/…

5/10

This study has the same methodology, and suffers from the same massive source of bias

Children (particularly young children) do not travel alone, especially during lock down in a pandemic

They are getting exposed at the same time as their close contacts (usually family)

6/10

The infected close contacts around same age are likely to be siblings who would be going wherever the index case is going, being exposed to the same sources of infection

It is impossible to tease out who the index case infected and who got infected at the same time as them

7/10

We can see from the graph that the older the children (and more mobile/independent) the lower the rate of associated positive close contacts were around the same age

Reduced "infectiousness" seems unlikely to be the cause

8/10

Now it may be the case that infected children are just as infectious; it has been difficult to determine

Indirect evidence from schools/family clusters with known direction of transmission has suggested not, but we can't be certain

This study doesn't get us closer

9/10

What we should have learnt by now is;

-These studies have massive bias for children which cannot be overlooked
-Single studies (no matter how big) should not influence policy without context of previous evidence
-In contact tracing, small and detailed beats big and dirty

10/10