Dr Zoë Hyde Profile picture
Oct 3, 2020 33 tweets 11 min read
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

Apr 21
@dtjohnso: I couldn’t reply for some reason so I’m writing this. You’re sort of on the right track, except new variants essentially mean immunity (to infection) is probably short-lived for many. (Immunity to severe disease thankfully is holding up better).
This means that all bets are off when it comes to herd immunity, and a good chunk of the population will probably always be vulnerable at any given moment (unless we can develop better vaccines). But we can still try to keep transmission low with better ventilation and the like.
Some measures like mask wearing could perhaps be dialled up or down depending on how much transmission there is. It will be crucial for governments to monitor this. Accessible testing is vital, but also things like sewage surveillance will be important.
Read 4 tweets
Mar 27
Groundbreaking new research shows a far-UVC (ultraviolet light) air purification system can reduce levels of an airborne pathogen by 98% within minutes.

This is equivalent to an incredible 184 air changes per hour - better than even HEPA air cleaners.
Researchers continually released aerosolised Staphylococcus aureus bacteria into a room ventilated with 3 air changes per hour.

This bacteria is harder to kill with UV light than either influenza or the coronaviruses that cause the common cold, making it a tough challenge.
After letting the bacteria fill the room for 60 minutes, the researchers then turned the far-UVC on (using 1 lamp or 5 lamps) at either low, medium, or high power.

Here are the results for 5 lamps:

Low power: 29% reduction
Medium power: 92% reduction
High power: 98% reduction
Read 5 tweets
Mar 13
I did an interview the other day in which I was asked when WA’s omicron wave will peak. Naturally, it’s something most people want to know, but in retrospect I think it’s the wrong question. Instead, we should ask how we can minimise the impact of the current and future waves.
The omicron wave won’t be the last. Why would it be? Look at the UK: the first wave of the original strain was followed by the alpha variant, then the delta variant, omicron BA.1, and now omicron BA.2. An average of ~100 people continue to die per day.
We can expect more waves in future, driven by waning immunity and/or the emergence of new variants.

If we allow high levels of transmission, we create the conditions for new variants to emerge. It’s a never-ending cycle, which harms lives and livelihoods.
Read 6 tweets
Mar 9
Younger kids now have to wear masks in Perth. How are they coping?

👧 “Really excited, ‘cause I quite like wearing a mask.”

🧒 “I’m kind of fine with it, but the mask is kind of sweaty on the inside.”

If this is the worst TV could find, I’d say most kids are doing just fine.
Most of the concern around children and masks is unfounded. If you explain why masks are needed in age-appropriate language, most kids will want to do the right thing and protect themselves and others.

Kids have a strong sense of fairness that many adults have sadly lost.
In the few, genuine cases where children struggle with a mask, exemptions can be made to excuse those children from having to wear one.

For the rest, masks may be a bit annoying at times, but it’s not forever, and better than ending up in hospital.
Read 5 tweets
Mar 9
A new study supported by the CDC shows that in 2021, there was more COVID-19 in US schools than the general community (see lines on the left).

But when masks were introduced at school, cases in schools plummeted (see lines on the right).
Both students and staff members were more likely to have COVID-19 than the general community, as shown in this graph (depicting the ratio of school to community cases).

The closer the curves are to 1 on the horizontal axis, the closer schools matched the general community.
The graph also shows that COVID-19 cases were lower in schools that required students and staff to wear masks.

The incidence was 23% lower in school districts that had a mask requirement.
Read 7 tweets
Mar 3
Today, Western Australia ended the border controls that have kept its people safe for two years. During that time, only 10 people died from COVID-19, making the state’s response one of the world’s best.
Unfortunately, the emergence of the omicron variant finally made Western Australia’s elimination strategy unviable.

Nonetheless, the Government continues to follow a suppression strategy for now. Better vaccines may make this easier in future.
I’m not concerned by the border reopening, because it will now make little difference to the trajectory of the omicron epidemic in Western Australia.

The most important thing was that we bought precious time to get third dose levels up.
Read 9 tweets

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