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COVID-19 Transmission and Children - Printable Version

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COVID-19 Transmission and Children - M_T - 08-18-2021

The journal research brief behind the current news can be found at the American Academy of Pediatrics site
"Association of Age and Pediatric Household Transmission of SARS-CoV-2 Infection"
(Free sign-in required to access full article)
And, separately,
Commentary:  "Yes, Children Can Transmit COVID, but We Need Not Fear"
WebMD coverage:  "Youngest Kids More Likely to Spread COVID-19 to Family: Study"

From the shortened version of the paper on the web site:

Quote:Results: A total of 6280 households had pediatric index cases, and 1717 households (27.3%) experienced secondary transmission. The mean (SD) age of pediatric index case individuals was 10.7 (5.1) years and 2863 (45.6%) were female individuals. Children aged 0 to 3 years had the highest odds of transmitting SARS-CoV-2 to household contacts compared with children aged 14 to 17 years (odds ratio, 1.43; 95% CI, 1.17-1.75). This association was similarly observed in sensitivity analyses defining secondary cases as 2 to 14 days or 4 to 14 days after the index case and stratified analyses by presence of symptoms, association with a school/childcare outbreak, or school/childcare reopening. Children aged 4 to 8 years and 9 to 13 years also had increased odds of transmission (aged 4-8 years: odds ratio, 1.40; 95% CI, 1.18-1.67; aged 9-13 years: odds ratio, 1.13; 95% CI, 0.97-1.32).


But, don't just stop with that paragraph.
From the actual paper (PDF)

Quote:Results:  Between June and December 2020, a total of 6280 private
households had a pediatric index case (Figure1).  The mean (SD)
age of index case individuals was 10.7 (5.1) years and 2863
(45.6%) were female individuals. Of 6280 households,
1717 (27.3%) experienced secondary household transmission,
leading to a median of 2 secondary cases (25th percentile,
1 case; 75th percentile, 2 cases; 90th percentile, 3 cases).
This corresponded with an overall crude rate of transmission
of 27 341 per 100 000 households with pediatric index cases.
Pediatric index cases most frequently transmitted infection to
individuals aged 0 to 20 years or 30 to 50 years, with older chil-
dren tending to transmit to older individuals in those age ranges
(Figure 2).
The proportion of index cases in each age group
increased with age, with 12% (776 of 6280) aged 0 to 3 years,
20% (1257 of 6280) aged 4 to 8 years, 30% (1881 of 6280)
aged 9 to 13 years, and 38% (2376 of 6280) aged 14 to 17
years (Table 1). Compared with index case indivudals in the
oldest age group, younger index case individuals had a
higher proportion associated with a school/childcare out-
break and shorter testing delays. Index case individuals aged
4 to 8 years and 9 to 13 years had higher proportion with no
symptoms reported compared with index case individuals
aged 14 to 17 years or aged 0 to 3 years. Across all age groups,
more index case individuals had disease onset in the fall/
winter (September-December) compared with the summer
(June-August), which aligns with the trajectory of the sec-
ond wave of the pandemic in Ontario.


So, the headlines are that infants infect others in the household more.  That's in the results in the web site but NOT mentioned in the results of the paper itself (but is in the discussion).   That is just one side of the elephant.

Another side is that the older children bring home COVID more often than younger children.
Index cases:  0-3: 766;  4-8: 1257;  9-13: 1881; 14-17: 2376

"Of 6280 households,
1717 (27.3%) experienced secondary household transmission,
leading to a median of 2 secondary cases (25th percentile,
1 case; 75th percentile, 2 cases; 90th percentile, 3 cases)."


Unfortunately, this neglects to tell us how many members were in the households.  Are these primarily 1 parent & 1 child household, or 2 parent & 10 children households?  Are they infecting virtually everyone or virtually no one in the household?

"This corresponded with an overall crude rate of transmission
of 27 341 per 100 000 households with pediatric index cases."


I'm going to have to figure out what they are saying there.

"Pediatric index cases most frequently transmitted infection to
individuals aged 0 to 20 years or 30 to 50 years, with older chil-
dren tending to transmit to older individuals in those age ranges
(Figure 2)"



Well, duh!  To me, their figure 2 bubble plot (age of secondary infected case vs age of index infected case) just shows the ages within families based on the age of one child taken at random.  It obviously shows 3 groups: siblings, parents&aunts/uncles, grandparents.  (At index age 17, it appears children of the index case (or niece/nephew) are starting to show up.)

The proportion of index cases in each age group
increased with age, with 12% (776 of 6280) aged 0 to 3 years,
20% (1257 of 6280) aged 4 to 8 years, 30% (1881 of 6280)
aged 9 to 13 years, and 38% (2376 of 6280) aged 14 to 17
years (Table 1)


The older the children are, the more likely they are to be the one to bring COVID into the house.  Again, they left out vital statistics indicating the Toronto population of children in each age group (note the age groups span 4, 5, 5, and 4 years).  So the rate of index cases (per population) is apparently much higher in the 14-17 than in younger ages, which makes sense as they have more social interactions and often ignore the rules. The (apparent) under-detection of asymptomatic cases in 14-17 suggests an even higher rate of that age group bringing the infection home.

Compared with index case indivudals in the
oldest age group, younger index case individuals had a
higher proportion associated with a school/childcare out-
break and shorter testing delays.


Yes, the oldest age group had more socialization, while the social interactions in the younger groups are more often just school.

 Index case individuals aged
4 to 8 years and 9 to 13 years had higher proportion with no
symptoms reported compared with index case individuals
aged 14 to 17 years or aged 0 to 3 years. 


No surprise here.  Ever try to get a mid-teenager or late-teenager to do anything, like take a COVID test?   Especially if one outcome will mean they are grounded for 10 days.   If you're the parent of a 0-3, you're probably frazzled and don't have resources to take them in for a test unless it is really bad (as happened in my extended family).   So, reduced testing, and thus detection, under no-symptom situations is not surprising to me.  Thus, you should expect a higher proportion of no-symptom positive tests reported in the more manageable adolescent years.

Across all age groups,
more index case individuals had disease onset in the fall/
winter (September-December) compared with the summer
(June-August), which aligns with the trajectory of the sec-
ond wave of the pandemic in Ontario.


Chicken and egg....  Let me rephrase it to give an equivalent expression:  The trajectory of the second wave in Ontario aligned with the detected pediatric index cases, showing more cases while school was in session.


RE: COVID-19 Transmission and Children - Hurlburt88 - 08-24-2021

This fall will be interesting.   THe school I was formerly on the board for is abandoning many COVID protocols, including masks.   I am worried someone in a downstream chain will get seriously ill.   

SEparately, I also wonder given viral loads of vaccinated people in first 6 days being almost the same as unvaccinated if boosters should be nasal vaccines to promote more mucous antibodies???