COVID: low transmission rates in schools

 A hopeful study from Wisconsin suggested that in-school transmission of SARS-CoV-2 can be significantly lower than in the community (see https://www.cdc.gov/mmwr/volumes/70/wr/mm7004e3.htm )

 

Details:

-- 4836 students and 604 staff members participated in in-person learning in 17 K-12 rural Wood County, Wisconsin schools, from September til December 2020

    -- 3 public school districts, one private school district, and one independent private school

    -- 8 schools were K-6 with 1529 students attending in-person, 9 schools were grades 7-12 with 3347 students attending in-person

    -- one school did not agree to participate, based on teacher preference

    -- 12.4% of Wood County children were attending school virtually

-- Wood County has a population of 73,000, 100 persons per square mile. 92% were non-Hispanic white, median income $55,000, 11% met poverty thresholds

--school infection mitigation measures: 2-3 layer cloth face coverings for all students, with a grant for students to receive 3 to 5 masks (schools were under district and statewide mask mandates during the study), mask wearing when students were within 6 feet of each other and at all times while indoors, a classroom cohort included students from one grade level who avoided mixing with other students, cohorts ranging in size from 11-20 students, all classes and lunch periods were indoors, students were seated near the same person within their cohort if possible, staff members wore masks, maintained a distance of 6 feet and had limited time in shared indoor spaces

    -- also, if a student were excluded from school because of Covid-19 symptoms, the student's siblings were also excluded from school.

-- No systematic Covid screening was conducted in the schools or in the community

-- school-attributable Covid-19 cases were compared to those of the surrounding communities

-- Masking was required for all students and staff members in all schools, with observed student masking compliance by teachers ranged from 92.1% to 97.4%, and this did not vary by student age

 

Results:

-- community SARS-CoV-2 transmission was widespread, with 7%-40% of Covid tests being positive

-- students and staff members at all schools: Covid-19 case rates were 191 cases among 5530 persons, translating to 3453 cases per 100,000

    -- of these 191 cases, only one in 20 cases among students were linked to in-school transmission

    -- no infections of staff members were found to have been acquired at school

-- County overall case rate: 5466 cases  per 100,000

-- within the schools:

    -- 5 case transmissions occurred within the elementary school, 2 in the secondary school cohorts

        -- 3 of the 7 cases occurred in one class in one elementary school, the other 4 in separate schools

    -- no in-school transmission between separate classroom cohorts was found

--[pretty striking graph. almost replicates the ones on the benefits of mRNA vaccines.....]

 

Commentary:

-- as a result of Covid-19, approximately half of students in the US have been receiving online instruction since March 2020

-- known downsides to closing schools reflect the strong relationship between education, income, and life expectancy:

    --economic analyses suggest that school disruptions from war and teacher strikes are associated with projected annual student income loss of 2 to 3% over the course of the affected students’ lifetimes

    --current economic models suggest that Covid-19 is estimated to diminish future earnings by $2.5 trillion!!! 

    --schools also serve many other social functions: they are an essential source of meals and nutrition for kids in K-12 as well as behavioral supports, physical activity, social interaction, supports for students with special needs, and other vital resources for healthy development 

    --the above findings are well-documented for school closings. the effects of morphing into off-site learning are likely less profound, though also likely highly variable by individual students, their abilities, home circumstances, home supports, length of time with off-site learning, ability of others at home to help when needed, access to computers and the internet, ......  And especially prolonged home-learning may well disproportionately affect and heighten the already existing inequities for kids from lower SES backgrounds

    --and, studies have documented the severe adverse psych effects of Covid-19 overall, and particularly in younger people: see http://gmodestmedblogs.blogspot.com/2020/08/covid-severe-psych-substance-use.html

-- this study found that there was a 37% lower Covid-19 incidence in schools having in-person instruction vs the surrounding community

-- of note, though students might be more likely to be asymptomatic carriers of SARS-CoV-2 virus, there were no student-to-teacher transmissions (though the study did not track all infection rates, including asymptomatics)

-- this study does undercut (to some extent) the statewide approach in the US of reopening schools based on a percentage of positive tests (typically in the 10% range), since in this study the community positivity rates range from 7% up to 40%. And still so few cases

-- there was a study in Norway in the summer of 2020, where there were significant increases in Covid-19 infections reported, assessing 2 populous counties with the highest Covid-19 rates. though infection rates in 5 to 13-year-old children were increasing, systematic tracing and testing of school contacts found low community transmission in the school setting (see https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.26.1.2002011;jsessionid=XJtPf50wnH_YvhDr9woWoYNt.i-0b3d9850f4681504f-ecdclive?fbclid=IwAR2XBDNzXyJfBcZ7aCslsmQAiBhqS57D738ab9gJpAz88_40lnvEE263CT0%23html_fulltext )

    --they systematically tested all contacts within the school twice during their quarantine period

    --an index case was a 5-13yo kid found who had been in school within 48 hrs before symptom onset or date of sampling

    --exposed child and adult contacts were identified, and they had testing right away and after a 10-day quarantine

    --most of their index infection cases were asymptomatic

    --and, of 234 child contacts, there were 2 cases (0.9%); of 58 adult contacts, there was 1 (1.7%)!!! [ie, almost no transmission]

--ironically/pathetically/pathologically amidst a SARS-CoV-2 surge in the US which far exceeds prior ones, some areas of the US are opening up bars, restaurants, etc but keeping their schools closed (seems like a pandering to COVID-fatigue in adults over the real potential devastation to the quite vulnerable, less-vocal and non-voting kids)

--there have been contrary reports on the viral transmission in schools, though the methodologies in the above studies were superior (eg, see http://gmodestmedblogs.blogspot.com/2020/08/covid-kids-as-vectors-school-closure.html 

 

limitations:

-- mask use was assessed by a non-validated survey, depending on voluntary teacher response and potentially subject to errors of recall and personal biases of teachers

-- there also might have been a bias because only half the teachers participated in the study

-- there were no data on masking compliance by staff members

 

So, interesting studies, with several suggestive conclusions:

-- the rate of documented in-school SARS-CoV-2 transmission was exceedingly low, much lower than the surrounding community

-- the generalizability of these results would require replication of a pretty aggressive monitoring within the schools to assure mask adherence, and the other risk mitigation strategies applied (there was no data available to suggest that any of the individual mitigation strategies would be sufficient)

-- also, there needs to be large buy-in by the teachers and administrators in order to implement a rigorous strategy

-- and, this all happened in a county that voted for Trump 60/40 over Biden... (ie, despite divisive politics that raised mask-wearing and even Covid-acceptance to high political levels, Wood County was able to get the vast majority of schools to accept a pretty aggressive infection mitigation strategy. though only half the teachers participated....)

geoff

 

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