I see people quite excited about a study of households in Wuhan, which suggested children and teenagers were less likely to get infected, but more likely to transmit than adults. However, there are some odd things about it, and I’m sceptical. Read on...
thelancet.com/journals/lanin…
The first issue, is that many people were not tested unless they had symptoms.

We know that children are more likely to be asymptomatic than adults and, lo and behold, children and teenagers were less likely to be tested than adults in this study.
The study was conducted between 2 December 2019 and 18 April 2020.

Prior to 23 February, testing was often symptom-based. Over 80% of cases occurred before this date, and just under half of contacts were not tested.
Supporting this, an unusually low proportion of secondary cases were asymptomatic.

Proportion asymptomatic by age:

0-19: 8.6%
20-39: 5.4%
40-59: 4.1%
>=60: 3.1%
But strangely, the data look even more odd after 23 February, when contacts were tested regardless of symptoms.
A greater proportion of asymptomatic cases were found in adults, which is not what you’d expect.

Proportion asymptomatic by age:

0-19: 15.3%
20-39: 21.2%
40-59: 16.8%
>=60: 12.5%
In the text, the authors note that the “pathogenicity of infection in children and adolescents (84·7%, 76·0–91·2 [83/98]) resembled that of adults aged 40 years or older.”

How did this not raise eyebrows?
This strongly suggests that many asymptomatic cases in children and adolescents went undetected in Wuhan, and casts doubt on the authors’ claim that children were less susceptible than adults.
It’s unclear what this means for the authors’ estimates of infectivity by age.
To be clear, I don’t doubt that infected children can and do infect their household contacts, but this study doesn’t help us better understand the risk.
Unfortunately, I don’t think this study adds anything new.

All we can draw from it, is that children and adults get infected with SARS-CoV-2, and they also transmit it to their household contacts.
We need better household studies, ideally prospective in nature, in which serial testing of all household contacts occurs.
Such studies should also take exposure into account. For example, by presenting attack rates for spouses of adult index cases separately from those of non-spouse adults.

Failure to do this makes differences in child and adult attack rates difficult to interpret.

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More from @DrZoeHyde

13 Jan
“How did it get transmitted? Was it in the air conditioning? Was it movement, was it picking up something? We just don’t know those answers yet.”

I think we do: #COVIDisAirborne.

No more mistakes. The UK strain (B117) isn’t forgiving.
#auspol #COVID19Aus
We’ve evidence to suggest the virus can be carried over long distances by air conditioning.

For example, in this study, viral RNA was detected in a hospital ventilation system more than 50 metres away from patients.
We also know that infectious virus can be cultured from air samples collected at a distance of at least 2 metres from people with #COVID19.

It’s not just fragments of viral RNA that can be found in the air, but complete, infectious virus.
Read 4 tweets
8 Jan
WA’s PPE guidelines are inadequate. Staff don’t have to wear masks if distance can be maintained, & bus drivers are only provided with surgical masks.

These are inadequate precautions for an airborne virus, and could lead to outbreaks.
#wapol #auspol
@CHO_WAHealth @MarkMcGowanMP
There are now numerous examples of aerosol transmission of SARS-CoV-2 around the world, particularly in enclosed environments such as buses.
Here is an example of aerosol transmission of SARS-CoV-2 occurring in a building:
Read 8 tweets
1 Jan
Anaphylactic reactions may be more likely with mRNA COVID-19 vaccines than other traditional vaccines (1 in 100,000 vs. 1 in 1,000,000); likely a reaction to carrier used to protect RNA component (polyethylene glycol, PEG), rather than the vaccine per se.
nejm.org/doi/full/10.10…
Persons with a history of allergic reactions associated with polyethylene glycol (or reactions to any of the other components listed) should avoid mRNA vaccines, and receive a different type of vaccine instead.
Note that other kinds of allergies (e.g., hay fever), are not expected to cause a problem.

There is no need to avoid the mRNA vaccines unless there is a specific history of allergic reactions to polyethylene glycol, or the other ingredients of the vaccines.
Read 5 tweets
30 Dec 20
The evidence is in, and the UK variant does appear to be of great concern. The viral load of infected people is higher, and it seems to be about 50% more transmissible. It doesn’t appear to cause more severe illness, but more cases will unfortunately result in greater mortality.
The estimated viral load of people infected with the new variant is substantially higher, although it is not yet clear why. Further laboratory studies will hopefully explain this.
medrxiv.org/content/10.110…
In contrast to early speculation, children do not appear to be markedly more susceptible to the new variant.
Read 9 tweets
18 Dec 20
(1/4) If I understand correctly, this is potentially dangerous. Rapid testing is to be rolled out in UK schools, but only staff are to be tested regularly. Students will only be tested if they are close contacts.
🔰 dfemedia.blog.gov.uk/2020/12/15/mas…

This has problems.

H/T: @dgurdasani1.
(2/4)

➡️ Both staff and students should be regularly tested. A proactive approach is required. Find the cases in students before they have a chance to transmit!

➡️ Primary school students should also be tested, not just secondary students. Young children transmit the virus too.
(3/4)

➡️ The rapid test to be used (a lateral flow test) has been shown to give false negatives half of the time.

Because close contacts will no longer quarantine under this programme, it’s likely some will go on to infect others.
bmj.com/content/371/bm…
Read 4 tweets
16 Dec 20
The latest round of random testing in the UK shows both children and teenagers are now more likely to be infected than adults.

1 in 48 teenagers and 1 in 58 children tested positive.

Infections are decreasing in adults, but increasing in children.

Red bar = most recent round.
The proportion of people testing positive by age group is as follows:

5-12: 1.7%
13-17: 2.1%
18-24: 1.0%
25-34: 1.0%
35-44: 0.8%
45-54: 0.8%
55-64: 0.7%
65+: 0.4%
In the accompanying media release the researchers note cases are no longer decreasing overall and:

“School-age children are ... the most affected age group, which could be linked to schools remaining open during lockdown.”

Link to media release & report: imperial.ac.uk/news/210873/co…
Read 4 tweets

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