Thread by @Theresa_Chapple

@Epi_D_Nique and I collaborated to provide a user-friendly review of the CDC’s study on #Covid_19 spread in elementary #schools in one Georgia district. This study is important because of its focus on young children and community spread. Happy🧵reading! cdc.gov/mmwr/volumes/7…

Data were collected over 24 school days (Dec 1-Jan 22, 2021) on Covid-19 spread in and outside of elementary schools, from Cobb County, GA. What’s interesting about this study? It focuses solely on elementary schools. Why is that important?

These schools serve the youngest group of school age kids, and some believe their contribution to Covid spread is negligible. We know that young kids have less extreme symptoms and lower risk of death compared to older children and adults.

Because of all those factors plus predicted impact of educational loss & lack of socialization, many push to allow the youngest age groups to fully #ReopenSchools. CDC guidance never suggests that elementary kids ever attend fully virtual school, even in the red zone.

This study shows elementary students can spread in schools & be the index case (first case starting the cluster). Data were obtained from 8 schools in one district. Pretty cool things they did- observed school mitigation techniques & collected self-reported data on it too.

Let’s review mitigation approaches- promotion of COVID-19 precautions outside of school, minimizing in-person adult interactions at school, ensured universal & correct mask use, physical distancing (3ft), & plastic barriers.

80% of the kids returned to school, space was an issue so schools did 3ft of distancing instead of 6. Teachers were close to students during small group work, mainly reading. Kids ate in their classrooms.

When a person tested positive for Covid (PCR or antigen), they either self-reported to the school or the school was notified by the health department. The school contact traced and contacts were advised to quarantine and test between day 5-10.

This is huge! This is one of the first studies that tested elementary age children that were quarantined. About 60% of those recommended for free testing, actually tested. Therefore, the data here could be underestimated, but we’re excited to see this much data presented.

Huge thing #2 this study looked at (limited) secondary contacts. For school spread cases, (index case infected another person at school), the investigators tested the household contacts. This provides insight into the question, does school spread contribute to community spread?

Huge thing #3, they actually tell us how they defined “close contacts” and the criteria for being a school-associated case! This is important because these details can be really important to what is found. More on that later.

What did they find- during the study 9 clusters (≥3 linked school-associated cases) were identified involving 13 educators and 32 students in 6 of the 8 elementary schools, all within 24 in-person school days (Dec 1 - Jan 22).

Teachers were the 1st identified case in 4 clusters, a student in 1, & in the remaining 4 a teacher & student were suspected. Teacher-Teacher spread followed by teacher-student spread occurred in 2 clusters which resulted in apx half of the spread in schools (15/31 cases).

Who infected whom? 8 of the 9 school clusters involved at least one educator & educator-student transmission. Also: 4 student-student, 3 student-educator, 2 educator-educator-student. So a whole lotta spreadn’ going on!

I thought there was mitigation? How did this happen? Breakdowns in mitigation. Breakdown #1- Because 80% of students were in person, < 3ft separation was possible. Plastic barriers between students may have helped but didn’t stop spread.

Researchers also suspect transmission between students & educators (7 clusters) occurred during small group instruction, where teachers were close to students. We guess that this happens in classrooms a lot, especially with the younger kids.

Although masks were mandated by the district, compliance wasn’t perfect. Reported & observed compliance was high, but in interviews it came out that students sometimes didn’t wear masks or didn’t wear them correctly (5 clusters).

Then there’s lunch. Lunch was suspected to contribute to transmission among both educators & students. Because, no masks. This has been found in other settings too (NFL study!). It’s a real problem for bringing anyone into buildings.

Speaking of the NFL study, that showed that transmission can happen in way less than 15 mins exposure. But the study used >15 mins per day (plus in 6ft) as the criteria for “close contact” which may have led to missed transmissions.

Did anyone bring covid home? YES. Free testing was offered to all home contacts who could be reached. 60% of all contacts were tested; 26% (n=18) were positive. This shows that schools can contribute to community spread.

Because the devil is always in the details, a few things to keep in mind when we interpret the results. Although this study makes some big advances in our knowledge, the lack of routine testing means not all cases were captured - especially for the students.

There were only 2 clusters where all of the spread was among children. It’s possible that teachers really are more likely to spread. It’s equally possible that spread among children wasn’t always identified since asymptomatic or very mild cases might not have been tested.

Speaking of testing! Routine testing could have prevented these clusters or at least limited their size. Clusters I & F, which show multiple transmission events, might have been stopped before they started if testing captured the index cases very early.

Kudos for reading this far. You get BIG TAKEAWAYS: 1. Transmission happens in schools even with mitigation 2. The more layers of mitigation, the more protection against spread when one layer fails 3. Ventilation/filtration is important for mask/distancing mistakes & meals

Takeaways cont: 4. Plastic barriers don’t replace distancing & ventilation 5. The more people in a building, the more virus in the air, both because there are more people in a room & more people = higher chance *someone* (or more than one someone!) has covid.

Final note: (at least) 14 cases came into the school which resulted in (at least) 63 more cases. Did schools contribute to community spread? Yes. Do family members of students & educators have reason to worry about infection? Yes.