One of the most debated and important issues concerning coronavirus disease 2019 (COVID-19) is the reopening of schools. The health, safety, and well-being of students, teachers, staff, and their families are critical considerations in determining whether schools should reopen for in-person learning.

Until recently, it has been thought that children were spared by severe illness, and in the majority of cases, children infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) only develop a mild illness; some are asymptomatic. One study looked at nearly 200 children who visited urgent care clinics or hospitals associated with Massachusetts General with suspected COVID-19, almost 50 of whom tested positive. Most of the children were not particularly ill, and only about half who tested positive had a fever.

While children represent only 9.1% of all cases in states reporting cases by age, over 406,000 children have tested positive for COVID-19 since the onset of the pandemic.However, 75,755 new child cases were reported from July 30 to August 7, 2020 (320,954 to 396,709), a 24% increase in child cases over two weeks.

A recent study shows that children carry high levels of the SARS-CoV-2 even without falling ill, which may impact the spread of the virus to others, especially those at high risk. The researchers also found that infected children younger than five years of age may carry up to 100 times as much of SARS-CoV-2 in their noses and throats as adults do, suggesting the possibility that the youngest children transmit the virus as much as other groups, even if they only develop mild to moderate illness.

One important strategy that school administrators can consider about opening schools is cohorting or forming pods, in which groups of students and sometimes teachers or staff stay together throughout the school day to minimize exposure. Ideally, students and staff within a cohort would only have physical proximity with others in the same cohort, which may help prevent the spread of the virus by limiting crossover of students, teachers, and staff. Since the virus is known to spread via respiratory droplets, it is important to address those features of schools that foster transmission, mainly, crowding.

Some schools that already reopened had to close within a week due to exposure to confirmed COVID-19 cases, indicating that detailed guidelines on both when to reopen and how to reopen are necessary.

A new study described a simple model that will help explore and understand variations in infection rates in both adults and children with different reopening approaches and criteria. The researchers based their analysis on an age-stratified assignment of all those in each school scenario into either 1, 2 or 3 groups. The age-based classification creates a cohort of adults and another of children. Each cohort is ascribed to homogeneous disease attributes.

Using a stratified Susceptible-Exposed-Infected-Removed model, they explored the influences of reduced class density, transmission mitigation (such as the use of masks, desk shields, frequent surface cleaning, or outdoor instruction), and viral detection on cumulative prevalence.

The aim of creating more than one cohort is to reduce student density in the classroom, thereby helping to analyze how re-opening at full capacity compares with re-opening at half-capacity with the remaining students continuing remote learning (parallel cohort strategy), or rotating cohorts between alternate weeks or three weeks. These are rotating cohorts.

The simulations in this study suggest that measures that reduce class density by rotating cohorts between in-person and online schooling are likely to have the greatest impact in reducing the spread of SARS-CoV-2 brought on by resuming in-person classroom instruction. The study model predicted that a combination of all three approaches will substantially reduce SARS-CoV-2 prevalence. The model also shows that reduction of class density and the implementation of rapid viral testing, even with imperfect detection, have greater impact than moderate measures for transmission mitigation.

According to the researchers, reducing the number or density of contacts produces a larger effect than diminishing the transmission rate per contact, findings that may help guide the public health policies regarding school reopenings.