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Andrew Lee Profile picture
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18 Feb, 16 tweets, 7 min read
Normally I enjoy the high standards of journalism in @guardian . Not today as disappointed with misleading headline that suggest infections are spreading fastest in children. It'll worry parents/teachers & I doubt most readers will unpick the headline.
1/
 theguardian.com/world/2021/feb…
The latest REACT1 report shows prevalence of infection in ALL age groups has fallen, including children aged 5-12 from 1.59% in Round 8 to 0.86% in Round 9a. The authors of REACT1 report also (wisely) didn't try to interpret the prevalence figures.
2/
 spiral.imperial.ac.uk/bitstream/1004…
If this were a research trial you wouldn't place much weight on the age differences in % prevalence because of the wide confidence intervals, i.e. differences weren't statistically significant.
3/
I've previously tweeted on the challenges (& dangers) of interpreting surveillance data. One would need lots more contextual info to make sense of it & arrive at sound conclusions.
4/
Undoubtedly some will extrapolate from the prevalence of infection figures in children to other settings i.e. schools based on the headline. I'd advise caution as there is a real risk of over-interpretation through extrapolation of limited data. Association is not causation.
5/
What REACT1 can’t tell us is how infectious children are or how much child infections drive the pandemic. Finding viral RNA on PCR from a child tells you nothing about how much virus they are shedding. Neither can it tell you the direction of transmisison (who infected who).
6/
Those of us in public health are well familiar with Bradford Hill criteria for causation that outlines key factors to consider. It would make sense to apply this approach to this issue.
7/
Is there CONSISTENCY? What’s been reported has been mixed, but @ECDC_EU , @CDCgov , @RCPCHtweets & other expert review groups have concluded the balance of evidence suggests kids aren't key transmitters of infection.


8/
Is the SPECIFICITY of the association or are there other confounders? Indeed the REACT1 report clearly show there are multiple other drivers such as deprivation & household size, etc...

9/
What about TEMPORAL SEQUENCE, i.e. does a rise in school outbreaks then follow a rise in community outbreaks? We aren’t seeing that.

10/
For me what also matters is PLAUSIBILITY & COHERENCE with what is known about the natural history and biology of the disease. Studies have shown that kids, being smaller, produce far fewer aerosols than adults. They also shed less virus than others.

11/
And also




And we know symptomatic persons shed more virus. So it follows that an adult is more likely to infect a child than the other way.
medrxiv.org/content/10.110…

12/
This isn't to say that infections from children to adults don’t happen. Of course they do, but at much lower levels than the other way around. We mustn't lose sight of the fact that adults still account for the bulk of infections.

13/
We know that of all settings, household transmission is the highest risk. If infection is introduced into the household the majority of household members are likely to get infected. Community transmission matters.



14/
This in no way refutes need for public health measures in schools to reduce risks of infection. Yes precautionary principle is important but need to balance both benefits & harms. Measures must be proportionate to actual (rather than perceived) risk.


15/
See also @apsmunro's excellent thread that outlines the evidence base.

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Andrew Lee Profile picture
17 Jan
I tweeted last week the link to @ECDC_EU evidence review of EU & international evidence on: COVID-19 in children and the role of school settings in transmission. Just finished reading it in full & it's balanced & comprehensive. (1) ecdc.europa.eu/en/publication…
Reiterates finding that children are very unlikely to have severe illness with COVID19 infection. (2)
Shedding of viral RNA thru upper respiratory tract may be of shorter duration in children than in adults. Associated with age, although doesn't appear to be significant difference in levels of viral RNA detected in nasopharyngeal swabs between the two. (3)
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Andrew Lee Profile picture
10 Oct 20
The number of COVID19 cases in UK continues to rise, with a trajectory that is worryingly becoming steeper. Hospitalisations up. ICU admissions up. Community transmission & outbreaks widespread. Clearly control of the epidemic in the UK is deteriorating. Deaths will follow.
1/
Worth revisiting @acmedsci 's report in July for their predictions. acmedsci.ac.uk/file-download/…
Their predicted real worst case scenario is looking more likely.
Give or take a few weeks, we're in for a difficult winter. What's less clear is just how bad is going to get...
2/
The UK gov has thrown £billions at the problem, hired loads of private consultants & consultancy firms, been given lots of good scientific advice, done national lockdown plus local variants of lockdown lite. Yet it's not working.
3/
Read 8 tweets
Andrew Lee Profile picture
1 Oct 20
The key to better control of the #covid19 pandemic may be in identifying & preventing #superspreading, through backward tracing to identify clusters. Need to rethink our approach.

Good article by @zeynep explaining the rationale.
theatlantic.com/health/archive…
Contact tracing seeks out where the infection has come from (look for source) & where it is going (contacts of the index who may be susceptible). An assumption is that all infections are equal (i.e. every infected person has a similar chance of infecting someone else).

1/n Image
So with COVID19, we assume with R0=2.6, 1 infected person infects 2.6 others. But this is an erroneous assumption if superspreading is a key mode of transmission. Some infected persons are more infective!

2/n Image
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