ON AUGUST 24, the Massachusetts Board of Elementary and Secondary Education approved a proposal by the commissioner of education to implement a mask mandate for Massachusetts schools that will last until October 1. Many parents, educators and legislators breathed a sigh of relief. Others are disappointed by the ruling. Proponents of mask mandates in schools rightly argue that the delta variant is more contagious than prior strains; that cases are relatively high; and that elementary students are ineligible for the vaccine. They point out that allowing only the vaccinated to unmask would be impossible to enforce.  

On the other side of the argument are those who support optional, rather than mandatory, masking in school. They (also rightly) point out that we do not know the extent to which masks might adversely affect language and social development, that controlled studies on effectiveness of masks in school are lacking, that children are at lower risk of severe disease from COVID-19, and that the World Health Organization, European CDC, and many countries have not recommended masks for younger children. Some also speculate that requiring vaccinated individuals to adhere to the same mitigation measures as the unvaccinated might negatively impact vaccine uptake.  

In contrast to what we saw a year ago, those in favor of school mask mandates and those against them are no longer split essentially along political party lines. Now, both sides can point to science – or lack thereof — to support their claims.  

By specifying a date at which the Massachusetts school mask mandate will be reconsidered, the Department of Elementary and Secondary Education is indicating to proponents of universal school masking that the danger of COVID-19 is being taken seriously, to opponents that mask mandates will remain data-driven, and to everyone that masks won’t be needed forever.   

We believe that “on-ramps” and “off-ramps,” developed based on scientific data, are the way to bring people toward a common middle ground. These pre-defined metrics would determine when risk of SARS-CoV-2 transmission is high enough that masks should be required, and when it has fallen to a sufficiently low level that masking could be optional.  

Why not just wait until a vaccine is available for all children? Let’s do a thought exercise. Suppose a vaccine had not been successfully developed (we know — a horrible thought) and was not even on the horizon. We would, in that situation, surely not expect masks to be worn in schools forever, but would at some point conclude that the level of danger has become low enough to remove mask mandates in order to normalize the educational experience. The timeline for vaccine availability for children under the age of 12 remains very uncertain. With the 5-week timeframe to full protection and the real possibility of slow uptake due to hesitancy, we cannot count on a high degree of protection from vaccination for children under 12 during the upcoming school year. 

The same criteria we would have used in the absence of a vaccine for young children might be used while we are waiting for one. So what should these metrics entail? Let’s look at some of the typical data elements used by Massachusetts public health officials to determine the need for restrictions and mitigation measures.  

Case rates: This is the most familiar metric used as a representation of the burden of infection in a community. When cases are low in a given town, COVID cases in school become rare and in-school transmission becomes unlikely. However, because the vaccines prevents severe disease with greater efficacy than they do mild and asymptomatic disease, cases have become decoupled from severe disease, and even more so in locales with higher vaccination rates, like many in Massachusetts. Case rates are also affected by testing volume, which changes over time based on a variety of factors. 

Percent test positivity: This metric is intended to assess adequacy of testing in a particular locale (when percent positivity is higher, it suggests that many cases are being missed). It is also largely impacted by testing volume, and has been shown to be significantly impacted by the presence of an institution of higher learning conducting regular screening in a community. Both case rates and test positivity are problematic because while students tend to live in the same town where they go to school, staff might live in towns with much different transmission rates. 

SARS-CoV-2 hospitalizations: This is a more reliable measure of the level of real danger from COVID-19 within a community, but still has flaws. Hospitalization numbers include patients admitted for COVID-19 and patients admitted with COVID-19 (who have asymptomatic or mild infection detected through routine admission testing but are in the hospital for another reason). This metric could be improved to better reflect severe disease by limiting it to patients who have impaired oxygenation or who receive therapy for COVID-19. 

Community vaccination rate: Although we have seen that even in locations with very high vaccination rates, outbreaks can occur, higher vaccination rates in a community have clearly been shown to increase safety by decreasing cases, hospitalizations, and deaths. In a town with a high vaccination rate, cases acquired in school have a lower likelihood of spilling over into the surrounding community. 

School vaccination rate: The higher the vaccination rate in a given school, the less likely an outbreak is to catch fire. Because vaccinated individuals are not required to quarantine when exposed, having a high rate of vaccination in school is also key to avoiding learning loss due to quarantines of students and staff (especially when combined with the state’s “test and stay” program, which allows unvaccinated students to go to school after an exposure by testing daily upon arrival). Disclosure of staff vaccination status, currently not mandatory in Massachusetts, is necessary in order to use this metric. The best way to protect the school community, though, is mandatory vaccination of staff. 

Our suggested path forward is to use a different combination of the above metrics for secondary schools where all students are of an age eligible for vaccination than for schools with a mixed age population. In the former, school community vaccination rate alone could be used to dictate the off ramp for masks. Based on estimates of the transmissibility of delta, an 80 percent vaccination rate (and acknowledging that among the unvaccinated, an unknown but non-trivial proportion have effective immunity from prior infection) provides a high level of protection against outbreaks. This is the metric currently being proposed by the Massachusetts Commissioner of Education and which Vermont has adopted.  

For schools with children under 12, we suggest using a combination of vaccination rate among staff and/or community case rate. The thresholds could be made easier to achieve for districts enrolled in the “test and stay” program which automatically achieves one of the goals of masking, avoidance of learning loss due to quarantines. Criteria should be met for two weeks before turning mask mandates “off” or “on.”   

Our proposal: 

  • For schools where an 80 percent vaccination rate is achievable (currently, high schools and some middle schools), a case rate that is moderate and falling or stable. Based on last year’s red/yellow/green model, masks could become optional when cases reach a moderate (yellow) level for two weeks and are not increasing. 
  • For elementary grades 2 and above and middle school: 80 percent vaccination rate of school staff and/or a low community case rate (green level) without test-to-stay, or a moderate case rate (yellow) if the test to stay program is available. 
  • For preK through grade 1, where there is a greater risk of impeding language and social development when teachers and students wear masks, 80 percent vaccination rate of school staff and a moderate (yellow) case rate, to balance the needs of early learners with SARS-CoV-2 transmission. In schools in which an 80 percent staff vaccination rate is not achieved, when cases reach a low (green) case rate, mask mandates could be removed for students and vaccinated teachers. 

For too long, we have lacked a light at the end of the tunnel – setting simple criteria that determine when mitigation measures are needed and when they are not would send a clear signal that life can look more like it did before March of 2020, which is something we can all look forward to. 

Shira Doron is an infectious disease physician and the hospital epidemiologist at Tufts Medical Center. She is an associate professor of medicine at Tufts University School of Medicine. Elissa Perkins is the director of emergency medicine infectious disease management at Boston Medical Center/Boston University School of Medicine, where she is an associate professor of emergency medicine. Westyn Branch-Elliman is an assistant professor of medicine at Harvard Medical School and an investigator at VA Boston. A major focus of her research is on implementation of evidence-based infection control practices in non-traditional settings, and de-implementation of ineffective interventions.