Post #1415: Virginia school reopening analysis

Posted on January 27, 2022


This post asks whether the January 2022 return-to-school has boosted the number of new Omicron cases in Virginia schoolchildren.  As far as I can tell, return to the classroom in January 2022 has had no material impact.  This is consistent with the fall 2021 return to school, where the resumption of in-person classes had no observable impact on the rate of new COVID-19 infections in Virginia children.


Last fall

Last fall, the return to in-person schooling in Virginia appeared to have no impact on the spread of COVID-19.  At that time, I tracked cases by age, and used the staggered start dates of the school districts as a type of “natural experiment”.  The idea was that if COVID-19 was spreading in the schools, you’d see the proportion of cases among school-age children rise, and you’d see that first where schools re-opened first.

But nothing happened.  At least, nothing that I could see.  Here’s the final graph from that analysis, Post #1280, 10/7/2021.

Last fall’s school reopening analysis:  No impact

Source:  Analysis of data from Virginia Department of Health, and school calendars from Virginia Department of Education.  This embodies a crosswalk of school district to Virginia health district.

That was almost entirely under the Delta variant.  Omicron only came on the scene as schools were finishing the fall semester.

A look at Spring 2022 using alternative data sources

Now schools are opening for the spring 2022 term under Omicron.  Omicron, recall, is about three times as infectious as Delta, and neither prior infection nor two-shot vaccination provides much protection against it.

In short, it’s a whole new ballgame.

I figured I should redo some version of that prior analysis.  But I can’t.  The data file I used for that no longer functions.  Virginia stopped updating the underlying file of cases-by-age last week, and now I know why.  Virginia apparently built up a huge backlog of cases with unknown age.  Last week, they corrected that and dumped the age-corrected cases into the file.  As a result, there’s no way I can see to calculate recent trends in cases by age, from Virginia’s current data.

There are, however, alternative data sources that provide some information on COVID-19 infections in the school population of Virginia.

Count of outbreaks

Outbreaks are defined as three or more related COVID-19 cases.  Virginia tracks outbreaks in a variety of high-risk settings including nursing homes, prisons, schools, and similar.

This isn’t a very quantitative measure.  It’s just the count of events that have been reported to the Virginia state government.  There are vastly more cases in schools than would be covered by the “outbreak” definition.

Source:  Calculated from Virginia Department of Health data.

That said, the number of daily outbreaks in Virginia K-12 schools is well within the historical level.  That’s actually a bit surprising, given how much the Omicron case level exceeds that of prior variants.  In any case, FWIW, the official count of outbreaks in schools is showing no red flags so far.

Pediatric share of Virginia hospital admissions.

Again, no indication of an uptick following resumption of classes in January 2022.

Source: Calculated from U.S. DHHS unified hospital dataset.

FCPS counts of infections

Fairfax County has the largest school system in Virginia.  Based on my analysis last year, Fairfax County Public Schools (FCPS) manages to count about 60% of all cases in school-age children (compared to the Virginia Department of Health data).  Arguably, then, Fairfax County is a pretty good bellwether for what’s happening in Virginia schools, even though snow delayed the start of school by about a week.

FCPS does not put out any raw counts, only pretty graphics.  All you can do, then, is eyeball their graph of cases in schools (top), against a similarly-scaled graph of all cases in Virginia (bottom).

There’s not a lot of precision there, and you have to ignore the one outlier day in the school counts.  But by eye, the case counts in the FCPS schools do not seem disproportionate to the counts for the Virginia population as a whole.


As far as I can tell, so far, from the available data, the January return to school has had no material impact on pediatric COVID-19 cases in Virginia.  At the very least, there’s been no large increase in any of the measures examined here.