How testing must be done to prevent school closings
Parents, educators and experts all agree; in-person learning is critical for students. Although there is widespread consensus on the matter, knowing how to achieve this and whether we can do it is hotly debated.
We face a daunting problem. In Toronto we are entering the new school year with a case rate more than four times as high as it was in September 2020 and a dominant variant that is five times more transmissible.
As in previous waves the impacts are asymmetrical. Community transmission rates are approaching or exceeding 200/100,000 cases in low-income, racialized communities but remain lower than 50/100,000 in the most affluent neighbourhoods.
While take-home testing will be made available for symptomatic students in public schools across the city, testing symptomatic children does not go far enough. Previous waves have shown that roughly one-third of infected children are asymptomatic. So, testing based on symptoms and exposure will under detect cases and will fail to prevent outbreaks.
Private schools with more flexible regulatory structures have done their homework. Many have opted for regular surveillance testing (two to five times per week) for students and staff using a rapid antigen test. Despite the lower sensitivity of the test compared to PCR tests, when used frequently, antigen tests reduce the risk of transmission and outbreaks. While private schools have made a smart choice, it also effectively created a two-tiered system of COVID-19 prevention within our schools.
In response, the Ministry of Education moved on Friday to limit their access to rapid antigen tests. A better move would have been to extend surveillance testing to public schools, most importantly to the elementary public schools, where students cannot yet be vaccinated.
Last year, two Toronto hospitals, Michael Garron Hospital and Women’s College Hospital with Unison Health implemented weekly or bi-weekly surveillance testing pilots in approximately 40 high-risk schools across the city. Cases were detected among asymptomatic children at a rate of between 0.5 and 3 per cent of tests. Principals, teachers and parents embraced the opportunity to prevent outbreaks through proactive testing.
A recent study from France using similar methods demonstrated that weekly screening of half the students with PCR saliva tests could reduce the number of cases by 24 per cent in the primary and 53 per cent in the secondary school contexts. Most importantly, regular screening would also reduce by 90 per cent the number of student-days lost compared to reactive class closure.
To avoid overloading labs, it would be necessary to only carry out surveillance testing in cases where the context and COVID rates warrant this measure. Schools can be prioritized for these programs based on known risk factors, such as vaccination rates, community prevalence and history of outbreaks.
Some advocates worry that surveillance in higher-risk schools will mean more exclusion of children who are exposed based on cases identified through surveillance. The solution to this problem is to allow children identified as exposed to an asymptomatic peer to remain in school if asymptomatic, with more frequent testing and enhanced infection prevention and control measures for two weeks from exposure.
Public health officials have also stated that every available dollar we have should be focused on vaccination, not testing. As we wrestle with vaccination rates that hover at 65 per cent in many areas, the reasons for getting vaccinated must be compelling, immediate and carried out by trusted partners.
The experience in the 40 schools that participated in last year’s efforts demonstrated that the surveillance programs built the trust necessary between clinicians and parents. These programs became an anchor for the vaccination clinics that have been operating from those same schools through the spring and summer.
The bottom line is that we need surveillance testing in high-risk elementary public schools. In the 2020-21 school year, outbreaks and closures in Toronto were predominantly in racialized and low-income schools. These outbreaks caused fear and anxiety among students and parents and ultimately tipped the balance toward system closure. Supporting these schools with special measures will support the system as a whole.