Can schools be opened safely, even when the COVID-1
Yesterday, the CDC published a detailed look at the spread of SARS-CoV-2 within a school system in Wisconsin. Although the results come from before the new, more easily spread strains were developed, they show that some of the measures set out in the guidelines for the safe opening of schools are working. Thanks to these precautions, infections at school have dropped by 37 percent compared to infections in the community as a whole, and there are very few infections at school. But it also raises an obvious question: if these measures work, why don’t we all use them?
The study started at the end of August 2020 and lasted until the end of November. It focused on schools in Wood County, Wisconsin, and traced infections that occurred among teachers and staff, as well as comparing those to the spread of the pandemic in the county as a whole. In total, the data include 4876 students and 654 employees.
The schools took many of the steps the experts had advised before the start of the school year. Each student was provided with multiple face masks when it started, and the use of masks was mandatory throughout the period. Compliance with this rule, based on teacher surveys, was consistently over 90 percent. (However, the report notes that not all teachers returned these reports, so data are likely to be missing in those classrooms where compliance was lower.)
In addition to masks, schools maintained small class sizes of 20 students or less. And these student groups were kept together throughout the day, instead of mixing during the day. All students who had symptoms of COVID-19 were sent home to be isolated, and all siblings they had were similarly prevented from attending school. The report does not say whether changes in classrooms – increased student separation or improved ventilation – are also included in the precautionary package. But in general, these policies are in line with the recommendations of health authorities for safe learning.
Out of control
And schools have been severely tested. As in most other states, COVID-19 cases in the county erupted in the fall. Sometimes Wood County has had a positivity rate of 40%, which means that four out of 10 SARS-CoV-2 tests are positive. This is taken as an indication that there are many more positive cases at the same time that have not been detected.
In general, the number of cases among students and staff is significantly lower than in the surrounding community. The percentage in the surrounding cities during the period was nearly 5,500 cases per 100,000 people. In contrast, students and staff had 3,450 cases per 100,000 people. This means a total of 191 cases: 133 for students and 58 for employees.
Contact tracking shows that only seven of these cases were taken through school transmission, all of which involved distribution among students. All seven of these cases are distributed among students in the same group in the classroom. In fact, three of them happened within a group in the classroom. The lack of dissemination between groups in the classroom is a reassuring confirmation of this strategy.
The biggest limitation of the analysis was that the testing capacity was clearly not sufficient to cope with the spread of infections during this study period. There is a very good chance that some asymptomatic cases will be missed at school during this period, which may affect the conclusions of the contact tracking experiment. As such, the seven cases allocated to the school should be considered as a lower limit.
There are several ways to view this data. The first few are obvious: it is not impossible to eliminate the risk during a pandemic out of control. But with appropriate precautions, it is possible to limit the risk to students and severely limit the chances of contracting new infections at school.
But the key message is that it is impossible to separate students from the larger community. While infections among students are declining compared to the wider population, a significant number of students have completed SARS-CoV-2 and most of these infections have come during interactions outside the school system. Which raises the obvious question of whether the wider population would benefit from adopting more of the practices used by schools.
As more and more infectious strains become widespread and the spread of vaccines struggles to move forward, it is extremely important that we accept everything that can be done to limit the spread in the meantime.