Can schools be kept open safely even as the COVID-19 pandemic continues largely unchecked? So far, the data has been mixed. Studies of spread in schools seem to suggest they’re not a major source of infections. But when countries that shut their schools as part of a package of pandemic restrictions were compared to those that didn’t, the ones that had schools shut down had a lower overall rate of infection. So, the record on opening schools seems a bit mixed.
Yesterday, the CDC released a detailed look at the spread of SARS-CoV-2 within a single school system in rural Wisconsin. While the results come from a time before the new, more easily spread strains had evolved, they show that some of the measures laid out in guidelines on how to safely reopen schools work. Thanks to those precautions, infections in the school were down by 37 percent compared to infections in the community at large, and there were very few infections that occurred within the school. But it also raises an obvious question: if these measures work, why aren’t we all using them?
The study started at the end of August 2020 and continued on through to the end of November. It focused on the schools of Wood County, Wisconsin, and tracked infections that took place among its faculty and staff as well as comparing those to the spread of the pandemic in the county as a whole. Overall, there were 4,876 students and 654 staff members included in the data.
The schools took many of the steps that experts had been advising in advance of the start of the school year. Every student was provided with multiple face masks when they started, and mask use was mandatory throughout the period. Compliance with this rule, based on surveys of teachers, was consistently above 90 percent. (The report does note, however, that not all teachers returned these reports, so there’s a chance that the data is missing those classrooms where compliance was lower.)
Aside from the masks, the schools kept class sizes small, at 20 students or fewer. And these student groups were kept together throughout the day, rather than intermingling over the course of the day. Any students who had COVID-19 symptoms were sent home to isolate, and any siblings they had were similarly kept from attending school. The report doesn’t have any information as to whether changes to the classrooms—increased separation of students or improved ventilation—were also included in the package of precautions taken. But overall, these policies are in line with the recommendations of health authorities for safe schooling.
Out of control
And the schools were put to a severe test. As with most of the rest of the United States, COVID-19 cases in the county exploded in the autumn. At times, Wood County had a positivity rate of 40 percent, meaning that four of every 10 tests for SARS-CoV-2 produced a positive result. This is taken as an indication that there are far more positive cases at the same time that weren’t detected.
Overall, case counts among the students and staff were significantly lower than in the surrounding community. The rate in the surrounding towns during the period was nearly 5,500 cases per 100,000 people. By contrast, the students and staff had a rate of 3,450 cases per 100,000 people. That translates to 191 cases in total: 133 in students and 58 in staff members.
Contact tracing indicates that only seven of these cases were picked up via in-school transmission, with all of them involving student-to-student spread. All seven of these cases involved spread between students in the same classroom group. In fact, three of them occurred within a single classroom group. The lack of spread between classroom groups is a reassuring validation of that strategy.
The biggest limitation of the analysis is that the testing capacity clearly wasn’t sufficient to have kept up with the spread of infections during this study period. There’s a very good chance that some asymptomatic cases were missed in the school during this period, which might influence the conclusions from the contact tracing part of the experiment. As such, the seven cases assigned to in-school spread should be viewed as a lower limit.
There are a few ways to look at this data. The first few are the obvious ones: it’s not possible to eliminate risk during an out-of-control pandemic. But, with appropriate precautions, it is possible to limit the risk to students and severely limit the chances of picking up new infections at school.
But the key message is that it’s impossible to separate the students from the larger community. While infections among students were down relative to the wider population, a significant number of students wound up with SARS-CoV-2, and most of those infections came during interactions that took place outside of the school system. Which raises the obvious question of whether the wider population would have benefitted from adopting more of the practices used by the schools.
With more infectious strains becoming widespread and vaccine distribution struggling to get ahead, it’s critical that we adopt anything that can be done to limit the spread in the meantime.