1. Updated thread on children & #COVID19 summarising the most recent research.

Summary: further evidence children & adults are equally susceptible & equally likely to transmit; school clusters are increasing; precautions needed in #schools.
#edutwitter #kinderen #Schulen #auspol
2. First, a recap, showing the risk associated with schools is largely dependent on community transmission.

If it is low (for example, at a level contact tracing can handle) then schools are low-risk (although precautionary measures are still needed).
3. Another large antibody study has shown that children and adults are similarly likely to be infected.

Importantly, young children and teenagers were just as likely to be infected.
4. This is similar to recent data from Italy.

In this household contact study in which people were tested for antibodies, there was no difference between very young children and older children.
5. This hasn't been seen in all studies. Here, younger children were less likely to be infected.

Circumstantial factors probably underlie such differences.

In this study, children were more likely to be infected if they were children of the index case.
6. Emerging data continue to suggest that children are as infectious as adults.
7. In the largest contact tracing study to date, a similar proportion of the contacts of child index cases and the contacts of adult index cases were infected.
8. This supports previous work from Italy, showing that the contacts of children were more likely to be infected than the contacts of adults.
9. Although it's not possible to say with certainty who infected whom in these studies, they strongly suggest that children do transmit the virus at clinically meaningful rates.
10. Even the youngest children can transmit the virus.

In this study, young children transmitted the virus to one-quarter of their household contacts.

Two out of three completely asymptomatic children transmitted the virus.
11. This is not surprising, because studies continue to show that children and adults have a similar viral load.

Here, the amount of viral RNA detected in swabs from symptomatic children was similar to (or higher than) that of adults.
12. Similar amounts of viral RNA were also detected in the swabs of children and adults in this study.

Importantly, no difference was seen in viral load between symptomatic and asymptomatic cases (which included both adults and children).
13. In this study of mostly adults, asymptomatic and symptomatic cases were also found to have a similar viral load.
14. This suggests children are likely to have a similar viral load to adults, even if they are asymptomatic.

This is important, because children appear much more likely to have an asymptomatic infection than adults.
15. In this antibody study of the children of healthcare workers in the UK, 50% of infections were asymptomatic.

Additionally, young (<10 years) and older (>=10 years) children were equally likely to have been infected (6.6% vs. 7.1%).
16. Infections in children may be hard to detect.

In this study from South Korea, 66% of symptomatic children with #COVID19 had symptoms which were mild enough to go unrecognised.

Only 9% were diagnosed at the time of symptom onset.
17. There may be little difference in symptoms between children with #COVID19, and those with other respiratory illnesses, as seen in this study.

The presence of fever or cough was not sufficient to distinguish between them.
18. This suggests it will be difficult to identify schoolchildren with #COVID19, and that schools will be an ideal environment for the virus to spread because of the number of close contacts that children have.
19. Although many cases in schools have been reported, there have been fewer superspreading events than was initially feared.

However, this doesn’t mean that children don't transmit the virus or that schools are a low-risk environment.
20. Two recent studies have shown that about 70% of infected people don’t seem to transmit the virus to anyone.

See the study below, and also the study described previously in point 7.
21. Exactly why is unclear. Possible reasons include the timing of infection, (lack of) opportunity to transmit, environmental factors that enhance transmission, and individual characteristics.
22. However, the frequency of transmission can be expected to be linked to the level of community transmission.

Higher levels of community transmission mean a greater probability of the virus being introduced to schools.
23. During a period of low community transmission in Germany, there was limited school transmission.

However, precautions were taken, including reducing class sizes by 50%, and regular ventilation of classrooms.
24. In the UK, the number of #COVID19 clusters in educational settings has surged since schools reopened.
25. Similarly, in France, clusters in schools and universities account for one-third of those currently under investigation.
26. Measures must be taken to reduce community transmission, and also to reduce the risk of transmission in schools.

At a minimum, this should include the use of face masks by staff and students (including both primary and high school students), and increasing ventilation.
27. Evidence continues to emerge of aerosol transmission being a major route.

This means that physical distancing - while important - is not sufficient.

Improving ventilation, wearing face masks, and reducing class sizes (if possible) are key.
28. There's growing evidence that masks protect the wearer from becoming infected, as well as preventing onward transmission.

Importantly, the kind of mask doesn't seem to matter too much, but it does have to be worn consistently.
29. If a school-aged child can safely wear a mask, they should.

Many Asian countries already require schoolchildren to wear masks, such as Singapore.

It is a simple intervention with minimal, if any, harms, as the Asian experience has shown.
30. On the other hand, if children are told they do not need to wear a mask in school and that they are unlikely to transmit the virus there, how can we expect them to behave outside school?

It seems unlikely they will follow precautionary measures. Advice must be consistent!
31. Even though children are far less likely than adults to become seriously ill, they can transmit the virus.

If we want to control the virus, we can't overlook the role of children in transmission.
32. We can't ignore any section of the population.

The virus doesn't remain confined to specific age groups.

In the US, a rise in cases in young adults was shown to precede cases in older people by about 9 days on average.
33. Schools remain an overlooked site of risk in many countries in this pandemic.

But guidelines to improve school safety have been developed.

If these guidelines (or those of a higher standard) aren't yet implemented in your region, ask why not.

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More from @DrZoeHyde

26 Feb
(1/22) Here's a new paper from me about some of the biases affecting research on children and COVID-19, and more importantly, some solutions.

It hasn't been typeset yet (the PDF might be hard for non-English speakers to read?), so I'll do a quick summary.
(2/22) First, "bias" has a different meaning in epidemiology compared to everyday life.

It doesn't mean someone's done something wrong. It just means there's a methodological issue that affects the results.

This article explains some of the common types.
(3/22) Now, on to the paper. It's been argued that children are less susceptible to infection with SARS-CoV-2 than adults and play only a minor role in transmission.

This conclusion is likely premature, because it's often difficult to detect infections in children.
Read 22 tweets
23 Feb
I don't like to dwell on negatives, but something important happened recently that I'd like to make public.

Shortly before Christmas, @mugecevik made a complaint to my university about me. When asked for details, she didn't provide any. My employer took a dim view of the matter.
I thought that was pretty strange, but laughed the matter off. After all, the complaint didn't go anywhere and I was supported by my university.

But last week, she made a complaint to a publisher about an article I recently wrote. It was this article:
She listed an astonishing 12 complaints (yes, 12!), said the article was grossly inaccurate, and asked for the article to be retracted.

However, no errors of fact were identified, so the article has not been retracted.
Read 8 tweets
22 Feb
Historically, I’ve not been a big user of social media. It never really appealed to me.

But in early 2020, I was pretty sure we were facing a pandemic and so started this account to share my thoughts with friends and family.

It got a bit bigger than I expected.
But as this account has grown, it’s taken up more of my time than it did in the beginning.

I don’t plan to stop tweeting any time soon, but I’m going to have to spend a bit less time on here. For one thing, it’s grant-writing season now, and that’s going to occupy me for a bit.
I’ve also begun to see how social media can be quite an addictive medium and I don’t want to get sucked into that. So I’m going to pull back a little in terms of the amount of time I spend on here.
Read 4 tweets
15 Feb
Here’s some good news. In this study of 514 people who received their first Pfizer vaccine dose, those who’d previously been infected showed a superior immune response compared to uninfected people, even if initial antibodies were no longer detectable.
Research has already shown that the vaccine acts like a super-booster in people who’ve been infected with SARS-CoV-2, suggesting that one dose may be enough for them.

However, it wasn’t clear if this would still apply if the antibodies from infection were no longer detectable.
This study shows that everyone got a boost, even if they no longer tested positive for antibodies.

A limitation is that the study only had 17 people with a previous infection (6 with detectable antibodies, 11 without), but the results are still reassuring.
Read 5 tweets
8 Feb
Thread summarising an important presentation on the AstraZeneca trial results for South Africa.

Key points:

➡️ Efficacy initially seemed to be ~75%, but dropped to 22% against SA 🇿🇦 variant.
➡️ Past COVID-19 (original) doesn't protect against reinfection by the SA 🇿🇦 variant.
This was a relatively small trial with only 1,749 mostly young, healthy participants.

People were given two doses of the vaccine about 28 days apart.
The relatively small number of people in the trial makes it suitable for exploring the efficacy of the Oxford/AstraZeneca vaccine against mild-to-moderate disease only.

The trial lacks statistical power to tell us the efficacy of the vaccine against severe disease.
Read 19 tweets
7 Feb
Australia must now reconsider its plan to use the Oxford/AstraZeneca vaccine, and instead use a high-efficacy vaccine like Novavax.

We've an agreement for 51 million doses of Novavax and can manufacture it domestically.
#auspol #COVID19Aus
According to preliminary results seen by the Financial Times, the Oxford/AstraZeneca vaccine does not appear to prevent mild and moderate COVID-19 caused by the South African variant.
While the company believes the vaccine may still prevent severe disease, there are now question marks as to whether it will be sufficient to prevent the debilitating condition known as long COVID, which is common even in mild disease.
Read 5 tweets

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