Here it is - a very interesting and compelling analysis of the incidence data by age groups in Montreal by @profSBVA, @olivierdrouin, Yacine Boujija and John Sandberg and @CovidEcoles.
It confirms infection incidence increased among younger age groups before it did in older populations - the phenomena that triggered all the 'casedemic' arguments we heard in late summer and early fall - which we now know were unfounded, as our hospitals face dark times ahead. Image
Importantly, it shows how much more dramatic the effect of unsafe school opening is in poorer neighbourhoods. In the lower income areas with large kid populations, the role of kids in driving the pandemic is crystal clear. Image
In the Centre-Sud (lower income, but not as many households with children), the picture is less poignant. Image
Whereas in the higher income area (Ouest), even though the proportion of households with children is as high as in the Nord and Est. Image
Within the areas where more than 30% of HH have children under 19, incidence increased first among kids 10-19 consistently, especially in lower income areas: ImageImage
A little less in middle-income areas. ImageImageImage
And not as much in Westmount and Pointe-Claire, in which although more than 30% of the HH have children under 19, are also two of the highest income areas in the city (median HH income above 100K/year). ImageImage
The incidence curves by age over time shows that the increase in incidence since schools reopened sustained increasing incidence among children 0-9 and 10-19, during Sept/Oct, creating a reservoir of cases that led to a dramatic increase starting in mid-November across all ages. Image
The effect of closing schools is also clear when we look at the incidence curves peaking on the week of Dec 29 and the subsequent sharp decline among children (and less sharp across other age groups) after the holidays. Image
Finally, I find the very compact area in the beginning of these curves quite compelling. Here we clearly see that as soon as schools opened (August 27th). Incidence among younger children (red line) started increasing consistently and only slowed during the December break. Image
Also, all other age groups (black arrows) had declines in incidence in Early October to mid-November, except children 0 to 9 and 10 to 19 (red arrows) and those over 70 years of age (orange arrow). Image
In short: "Looking at the evolution over time of new cases of COVID-19 by age group in Montreal during the fall quarter of 2020, our first observation is that, even at young ages, children do contract VIDOC-19 and account for a significant portion of the confirmed cases."
"Second, our descriptive analysis shows that the incidence of COVID-19 among children aged 10-19 years did not follow, but rather preceded, the increase in adult cases. aged 30-49 years old. "
"As a result of this trend, at the beginning of January 2021, adults aged 30-49 and children aged 0-19 represented, respectively, 31% and 21% of the total number of confirmed cases in Montreal. "
"In other words, the transmission of COVID-19 in school-aged children does not appear to be a consequence, but rather an important determinant, of the level of infection in surrounding communities."

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More from @DGBassani

4 Jan
Are you ready to see hell breaking loose? It already started, but will become undeniable soon. We’re about to leave the 3K/day behind and move on to the next level of horror. The climb will be faster than ever. Watch the UK for a preview. And remember this the next time you vote.
The ON government will try to again, blame the people, but this is all on them. The Ontario government dismantled its public health agency during the years leading to this pandemic.
We’re in this situation because of Ford’s failed communication strategy during the pandemic, MoH’s failure to invest in the necessary test and trace capacity during summer, and the MoE lack of plan for a safe school restart last fall.
Read 7 tweets
18 Dec 20
This corresponds to a prevalence of 1,583 cases per 100,000 asymptomatic individuals. It is extremely high for an asymptomatic population. There are currently 2,703 active cases in the population under 20 years of age in ON. These were found by testing ~45,000 symptomatic people.
The resulting prevalence is ~6,000 cases / 100k ppl with symptoms tested. Since ~55% of the cases in this age group are symptomatic, and if we assume all symptomatic kids were tested (not true), we can expect to find another 2,200 cases among the untested ON population <20 yrs
Read 12 tweets
18 Dec 20
Time for this again? I don’t know by which standard 1,580 cases/100,000 people is low. That is what 57 cases in 3,600 asymptomatic tests corresponds to. This is the asymptomatic population prevalence. It is very, very high.
There are 194 active outbreaks in ON schools, from the official data from the ON situation reports. Second only to workplaces (230). There are 54 in recreational facilities and 20 in ‘other’.…
Read 8 tweets
17 Dec 20
I have been writing this thread over the last few weeks, as I have been trying to understand what is going on with the trends observed for the core triad of community infection indicators in ON: positivity rates, test volume and new cases and I think I have an hypothesis.
I now updated the graphs and will share it as others may have ideas about what is going on:

First, the trends on these indicators in ON:

Cases - Non-stop growth since early September.
Testing: Since testing strategy changed (Oct 5th), daily test volumes increased for about 1 week and then declined from ~43K to ~33K (7d averages).

Positivity: 7d average increased from 0.5% on Sept 1 to 3.9% on Nov 14th.
Read 23 tweets
17 Dec 20
They need to do this, because the fall strategy led to rampant infections in this province. It seems we’ll close schools with little warning, and with no plan for the next 6 months. This will not take us very far.
Elderly are dying because kids are bringing virus home and there is no testing or contact tracing. See this - it illustrates the magnitude of the problem:
To assume closing currently unsafe schools is a more damaging option than keeping them open under the current circumstances. It is also selfish ageism. It places higher value on the school experience for children than the lives of elderly and the strain on the health care system.
Read 6 tweets
13 Dec 20
Why are cases surging? I’ll answer my own question. A thread 🧵:
We are in this situation because all logic about how an epidemic progresses was ignored for months and the concerning reservoir of hundreds of cases from summer was left unchecked with no critical pushback and advocacy for prevention by most health professionals.
The needed expansion of the testing/lab capacity was scrapped to cut costs. Very few complained as it happened. The lack of TTI planning for the certain fall surge was a very shortsighted move. But how dare you close schools early or extend the break?
Read 13 tweets

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