These are extraordinary times.
When the COVID-19 pandemic hit the United States in force in March 2020, every state closed its schools in response, disrupting the education of over 60 million children. Globally, 1.2 billion students, 67.7% of the global student population, were affected by school closures as of late May. Districts are now considering reopening schools due to the detrimental effects of closures on the long-term well-being of children and the ability of their parents or caregivers to effectively return to work.
School closures reduce expected student learning gains, which can have lifelong consequences and exacerbate educational and economic inequalities. The amount of learning loss due to physical school closures varies by access to remote learning, the quality of remote instruction, and the degree of student engagement. Low-income students are less likely to have access to high-quality remote learning opportunities. Greater learning loss of Black, Hispanic, and low-income students could increase the existing educational achievement gap in the United States by an estimated 15 to 20%. Beyond learning loss, COVID-19 closures will likely lead to an increase in the rate of high school dropouts. And even for students who stay in school, delaying school reopening until 2021 could lead to reductions in lifetime earnings of 1.6%, 3.3%, and 3.0% for white, Black, and Hispanic students, respectively, over a 40-year working life.
School closures may also result in negative impacts on students’ current health and safety. For example, a UNICEF report raised awareness that children are at greater risk of abuse, neglect, exploitation, and violence due to lockdown measures.
There is also a concern regarding impacts to physical health. Studies have found that students are increasingly sedentary the longer they are on school break and tend to experience unhealthy weight gain outside of school terms. As physical activity participation and weight status track into adulthood, there are potential lifelong health impacts of closing schools. COVID-19 school closures could increase weight gain due to reductions in access to physical education classes, outdoor spaces for physical activity, and food security for students relying on school meals.
School closures reduce expected student learning gains, which can have lifelong consequences and exacerbate educational and economic inequalities.
In addition to negative impacts on students, school closures prevent parents and caregivers – including potentially 30% of healthcare workers – from fully returning to work. Healthcare workers responsible for infection control in nursing homes, where COVID-19 risk is very high, are among the most highly affected by childcare obligations from school closures. Though school closures are intended to help slow the spread of COVID-19 to reduce the strain on healthcare, they may also serve to reduce the healthcare workforce itself.
Even if school districts decide that the societal benefits of opening schools outweigh the risks, reopening schools will not be easy. And disruption and future school closures may be necessary. There are examples internationally of schools reopening but then having to close a second time after it appeared that local COVID-19 case counts were rising. However, schools can implement concrete strategies to minimize the risk of COVID-19 outbreaks and to keep students and staff as safe and as educationally productive as possible.
The transmission of communicable diseases can occur in school environments. Outbreaks of diseases such as chickenpox, measles, mumps, scabies, acute hemorrhagic conjunctivitis (pink eye), and norovirus in schools have all been well documented in the scientific literature. In some cases, outbreaks have occurred even in populations of school children with high vaccination rates.
There are several reasons why disease outbreaks occur in school environments. Research shows that disease outbreaks can happen when immunization against a disease is not 100% effective, when there is vaccination failure, or when there is an inadequate level of immunity in some of the students. Furthermore, the high degree of interaction of students in schools and the frequency with which children put their hands or objects in their mouths increase the transmission of disease.
Even so, historical disease outbreaks in school environments indicate that implementing adequate intervention strategies can successfully minimize COVID-19 transmission and keep students safe when reopening schools.
As schools develop plans for reopening, we must all recognize that the safest way to reopen schools is to do so with COVID-19 cases under control. This requires a cohesive national response that is not yet operating across the U.S. There is a way to do this, and we must act now. With other colleagues at Harvard T.H. Chan School of Public Health, the Healthy Buildings program released a project, COVID Path Forward, that outlines 14 priority areas for saving lives and the economy. To track progress on each of the 14 Priority Areas, including Priority Area 10, which focuses on schools reopening, visit: www.CovidPathForward.com.
Schools should err on the side of caution when it comes to health and safety. Children generally have less severe COVID-19 symptoms than adults, but they are not immune. Children can become severely ill with COVID-19, and they are capable of transmitting the virus among themselves and to family members or teachers. Older adults are at greater risk of severe COVID-19 illness. On the other hand, schools, teachers, administrators, and parents must also recognize that there is no ‘zero risk’. Reopening schools will require accepting that the goal is risk and harm reduction.
No one control strategy alone can limit the transmission of disease. Schools should approach reopening with a layered defense strategy, where many small interventions and strategies are combined, simultaneously. Schools should deploy an ‘all in’ approach that uses every control feasible.
Just as there is no single control strategy that is effective in and of itself, there is no single entity that is solely responsible for keeping everyone safe. Successfully reopening schools will require continual collaboration between administrators, staff, and teachers and ongoing cooperation among teachers, students, and parents. Everyone has a critical role to play. Getting through this pandemic will require a great deal of social trust.
Even with the best control strategies in place, there will be cases in some schools. To limit classroom outbreaks from becoming school-wide outbreaks, schools should take steps to limit contact chains as much as possible. Within a district, school populations should not be mixed. Within a school, classes should be kept separated as much as possible. Within a classroom, kids should be physically separated as much as possible.
The scientific community’s understanding of this virus is changing rapidly. Disease spread and timing are not fully predictable. Schools should recognize that the dynamic nature of knowledge during a global pandemic requires a flexible and adaptive approach. The strategies in this report were developed with careful attention to the most recent scientific discoveries regarding COVID-19 and its effects on and transmission among school-aged children. Our collective understanding of this virus will change, and therefore the approach schools take may change over time, too.
School closures have disproportionately impacted children of lower socioeconomic status, children with disabilities, and children in other marginalized groups. The reopening of schools must be done with equity in mind. Some challenges to ensuring equity in schools during the current pandemic that should be addressed when developing plans to reopen include:
COVID-19 is the disease caused by the SARS-CoV-2 coronavirus. Before we talk about specific reopening strategies, it is useful to recall how the COVID-19 virus spreads so we can understand when and how a specific intervention might be effective. There are three routes of transmission for COVID-19 that are supported by models and case studies of outbreaks.
Close-contact transmission can occur via droplets (> 5 μm in diameter) or aerosols (tiny droplets < 5 μm in diameter, also called droplet nuclei). Close contact transmission by droplets refers to close-range transmission of virus by sometimes-visible droplets that are coughed or sneezed by an infectious person directly onto the eyes, mouth, or nose of a nearby person. Droplet transmission can be minimized by, among other things, physical distancing and universal non-medical cloth mask-wearing. Close contact transmission by aerosols refers to transmission of virus in tiny, invisible droplets that are generated when an infectious person exhales, speaks, coughs, sneezes, or sings, and that are then inhaled by another nearby person, allowing the virus to deposit directly on the surfaces of their respiratory tract. This close contact aerosol transmission can also be minimized by, among other things, physical distancing and mask-wearing.
Long-range transmission refers to transmission of virus in aerosols, which may be generated when an infectious person exhales, speaks, sneezes, or coughs and then travel out of the immediate 6-foot vicinity of the infectious person via airflow patterns. This airborne virus can remain aloft for more than an hour indoors to infect people who are not interacting closely with the infectious person. Long-range airborne transmission can be minimized by, among other things, increasing outdoor air ventilation to dilute the concentration of airborne virus or filtering air recirculating in a room or building.
Fomite transmission refers to viral transmission via inanimate objects, like desks, tables, playground equipment, or water fountains that are contaminated with the virus. A surface could become contaminated in many ways, for example, after a person coughs directly onto an object or after they sneeze into their hand and then touch the surface. Individuals who touch the fomite while the virus remains viable, and then touch their eyes, nose, or mouth before washing their hands, could be exposed to the virus. How long the virus can be detected on fomites depends on the type of surface and the environmental conditions. Under some conditions, the COVID-19 virus can be detected up to 72 hours after deposition on hard, shiny or plastic surfaces or up to 24 hours after deposition on more porous surfaces, but the risk posed by these day(s)-later detections is much lower than the initial risk because the amount of the detectable infectious virus decreases rapidly over time. Fomite transmission of a virus can be minimized through frequent cleaning and disinfection of commonly-touched objects, through use of automatic or touchless alternatives (e.g., automatic doors), and through frequent hand washing.
There are three components of exposure – intensity, frequency, and duration. In general, more intense, more frequent, and/or longer duration exposures have the potential to cause more harm. In the case of COVID-19, we can reduce the risk of illness through interventions that reduce any or all of these three characteristics:
Intensity of exposure to SARS-CoV-2 may be minimized by physical distancing because the amount of SARS-CoV-2 in the environment around an infectious person is highest closest to the infectious person. Additionally, infectious people following respiratory etiquette (i.e., cover nose/ mouth when coughing or sneezing) and wearing masks reduces exposure intensity to people nearby.
Frequency of exposure to SARS-CoV-2 may be minimized by reducing how often someone is in close contact with individuals outside the home who may be infectious.
Duration of exposure to SARS-CoV-2 may be minimized by spending less overall time inside in close contact with others.
While exposure is largely a function of intensity, frequency, and duration, risk is determined by many additional factors. Most importantly, personal risk is dependent on individual susceptibility. For example, this may be a function of age, gender, pre-existing conditions, or genetics. For these reasons, two people with the same exposure may have very different risk. Discussions of risk can also be subjective, in that they depend on personal risk tolerance. Last, risk is a function of factors outside of the individual, including the local healthcare capacity, the efficacy of available treatments, and the extent of spread in the underlying community.
Two people with the same exposure may have very different risk.
Existing research indicates that children are less susceptible to COVID-19 than adults. Studies based on contact tracing data from Asia, PCR test results from Israel, serum antibody test results from the Netherlands, and mathematical modeling using data from six countries suggest that children are approximately half as likely as adults to become infected with COVID-19 after being in close contact with an infectious person. Older adults are more susceptible to COVID-19 than younger adults. Analysis of serum antibody data from households from the Netherlands found that 1- to 5-year-olds were 32% less likely than 18- to 45-year-olds and 51% less likely than 45+-year-olds to get COVID-19 from an infectious family member.
Symptomatic children often experience many of the same symptoms as adults, including fever, cough, and fatigue, along with nasal stuffiness, rhinorrhea, sputum, diarrhea, and headache. Compared to adults, children have more upper respiratory tract involvement (including nasopharyngeal carriage) rather than lower respiratory tract involvement, and prolonged viral shedding in nasal secretions and stool.
In general, COVID-19 appears to be less severe among children than among adults. The infection fatality rate (IFR), the number of deaths per infection, is a useful metric for comparing the severity of COVID-19 infection across groups. A recent study of Geneva, Switzerland, found that individuals younger than 50 years of age had lower IFR values (ranging from 0.00032-0.0016%) compared to individuals aged 50-64 years (0.14%) and 65+ years (5.6%). Similar metrics measured in Hubei province, China, and northern Italy also found that adults with COVID-19 were more likely to die from COVID-19 than children.
In general, COVID-19 appears to be less severe among children than among adults.
While severe cases of pediatric COVID-19 are reported to be rare, some groups seem to be at elevated risk of negative outcomes. Children with comorbidities, such as pre-existing cardiac or respiratory conditions, may be at a higher risk for severe COVID-19 requiring hospitalization. Furthermore, it has recently been suggested that previously asymptomatic children may develop a hyperinflammatory syndrome with multiorgan failure. Finally, it is not yet known whether COVID-19 may have long-term negative health outcomes for children. Severe acute respiratory syndrome (SARS), another respiratory virus, was found to have negative impacts on children’s aerobic capacity 15 months after they were ill. Therefore, while children comprise a small fraction of global COVID-19 cases and their symptoms are often mild, the potential for negative health outcomes in children due to transmission in schools cannot be discounted.
The incubation period of a disease is defined as the time from exposure to a disease-causing agent to the time when clinical signs of a disease first appear. This period may vary between individuals and is often reported as a range. For COVID-19, the average incubation period is around 7.7 days in children and 5.4 days in adults but can range to up to 14 days.
It is possible for individuals to spread COVID-19 prior to experiencing any symptoms. Studies suggest that transmission of COVID-19 can occur as early as five days before onset of symptoms. For mild cases not requiring hospitalization, studies suggest that an individual is no longer able to transmit disease ten days after first experiencing symptoms (as long as they do not have a fever and have improved clinically). Severe COVID-19 cases may have a longer infectious period; one study found that the infectious period among 129 severely or critically ill hospitalized patients ranged from 0 days to 20 days after symptom onset with a median of 8 days after onset. According to the World Health Organization (WHO), two consecutive negative laboratory test results, taken at least 24 hours apart, can be used to determine the end of the infectious period.
Studies of households indicate that transmission from children to other children or to adults is much less common than transmission from adults to children or transmission between adults.
Children’s ability to transmit COVID-19 (“infectivity”) is dependent on their susceptibility to infection, development of symptoms, viral load, and their risk factors for exposure and for exposing others. Contact tracing studies indicate that children were the index case (original infected person) less than 10% of the time, although further analysis accounting for asymptomatic children suggests 21% of cases could be attributed to transmission by children. Studies of households indicate that transmission from children to other children or to adults is much less common than transmission from adults to children or transmission between adults. For example, in a study in Chicago, children were responsible for 26% of secondary cases, spreading the virus both to other children and adults; in a larger study in the Netherlands, children were responsible for <5% of secondary cases and again spread the virus to other children and to adults.
One potential reason for reduced infectivity of children is their reduced susceptibility to infection, which would reduce their overall likelihood of acquiring and transmitting the virus to others.
While children can clearly transmit the virus to others and despite some evidence of prolonged nasal or fecal viral shedding in children, infectivity is reported to be lower in youth compared to adults. Preliminary models estimate that infectivity of children is 85% that of adults. In the limited available data in schools, transmission between children has also been reported to be low.
One potential reason for reduced infectivity of children is their reduced susceptibility to infection, which would reduce their overall likelihood of acquiring and transmitting the virus to others. While asymptomatic or mild cases can certainly spread COVID-19, the generally less severe symptoms in children may also reduce infectivity by not producing as many large droplets or aerosols via talking/coughing/sneezing.
Regardless of children’s susceptibility to infection, symptom severity, and viral load, there are unique behavioral factors in this age group that can facilitate the spread of infectious disease, including the large number of contacts of school-aged children and the frequency with which children, particularly young children, put their hands or objects in their mouth. In the absence of further scientific knowledge about COVID-19 transmission among and by children, particularly in school settings, it is reasonable and prudent to assume that COVID-19 transmission may occur between children and from children to adults in reopened US schools.