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I live with someone who hasn’t been vaccinated against Covid-19. He’s my first-grader.

Like all of his classmates and anyone under 12 years old, Davi can’t yet get one of the authorized vaccines. But as schools return to full-time in-person learning, they are doing so in the face of a rapidly rising fourth wave of the pandemic that is affecting mainly unvaccinated people. And because the prevailing Delta variant is so highly infectious, more young children are being diagnosed with Covid-19 than in the previous waves.

Many parents and school administrators are faced with a dilemma of growing urgency: How do we ensure that kids are safe at school while still reaping the benefits of in-person learning?


To answer this question, my colleagues and I at Color, in collaboration with modeling experts Carl Bergstrom and Ryan McGee from the University of Washington, built an interactive model that simulates the course of an outbreak after an infected person enters a congregate setting such as a school or workplace. Users can vary how often teachers, staff, and students are tested, how infectious the virus is, vaccination uptake by teachers and staff, and vaccine effectiveness.

Color interactive model
The result of one model generated by the interactive app developed by Color and University of Washington experts. Image courtesy of Color

The example above from the app compares three testing scenarios with a highly infectious virus (reproductive number = 3.5), 60% of teachers and staff vaccinated, and a vaccine effectiveness of 90%.


The K-12 school model, which was published as a pre-print and will be publicly available soon as a peer-reviewed publication, shows that reducing the risk of an unrestrained outbreak requires using multiple mitigation efforts. (At the time the paper was published, the Delta variant was not yet widespread. We later updated the interactive app to reflect the infection dynamics of the Delta variant).

The results of the model are clear. Four measures must be implemented in parallel to minimize the chances of school-related outbreaks.

Require vaccination. The currently authorized Covid-19 vaccines are safe and incredibly effective against Covid-19. Though they have not yet been authorized for use in those under age 12, ensuring that every eligible individual within a school is vaccinated is one of the best ways to protect the entire school population. High vaccination rates in teachers, staff, and students over the age of 12 will not only protect the vaccinated individuals, but will also benefit those who aren’t able to be vaccinated, such as children under 12 or those with specific medical contraindications.

Wear masks. If someone in a school has been infected with SARS-CoV-2, the best way to minimize others’ exposure is to ensure that all individuals are wearing masks. This is especially important given that some individuals may not show any symptoms but can still transmit the virus. Masks are one of the most effective tools to prevent person-to-person spread of Covid-19. They are simple, cheap, and effective. Until case counts come back down and community spread is once again low, all individuals in a school — students, teachers, staff, visitors, and others — should wear masks indoors to ensure a safe learning environment.

Increase ventilation. Early in the pandemic, researchers learned that the major form of SARS-CoV-2 transmission is through droplets, and sometimes even aerosols. In addition, many case studies have shown that transmission is much less likely in outdoor settings than in indoor settings. To mitigate and reduce the likelihood of droplet and aerosol transmission, schools should consider the CDC guidelines that recommend updating heating, ventilation, and air conditioning systems to increase airflow, including the use of high efficiency particulate air (HEPA) filters, and increasing the introduction of outdoor air.

Get tested. The Delta variant is two to three times more transmissible than previous versions of SARS-CoV-2. Until children under the age of 12 can be vaccinated, it is impossible in elementary school settings to achieve herd immunity through vaccination. Although partial adoption of vaccination in the school community is helpful, proactive frequent and fast testing is an effective way to quickly identify, isolate, and contain potential school-related transmissions. Weekly or twice weekly testing of all students, teachers, and staff can hugely reduce the likelihood of school-related outbreaks.

The pandemic has forced us to quickly adapt our expectations and our behaviors. As a parent who watched an entire year of distracted and isolated distance learning go by, I know how important in-person socialization, communication, and education is to kids’ emotional development and mental health. Life hasn’t been easy for adults or children since March 2020.

In-person learning is not only an essential construct for children’s education, it is also an important keystone that holds together today’s workforce. As I and many others learned firsthand, it is unsustainable to have two working parents in a household while also supporting one or more distance-learning children. In far too many cases, one parent (most often the mother), sacrifice work productivity to be able to juggle everything. As a result, women account for a disproportionate number of job losses during the pandemic. Managing distance learning is even more of a struggle in single-parent households. Many single parents have had to find creative ways, like changing their working hours, to juggle both their parenting and professional responsibilities.

Getting kids back to school this fall will take a combined effort from parents, students, teachers, and school administrators. The good news is that we already have the tools needed to get there.

Now we just need to use them.

Alicia Zhou is the chief science officer at Color, a health technology company that makes population-scale healthcare programs like COVID-19 testing and vaccination initiatives.

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