It is critical for schools to open as safely and as quickly as possible for in-person learning. To enable schools to open and remain open, it is important to adopt and correctly and consistently implement actions to slow the spread of SARS-CoV-2, the virus that causes COVID-19, not only inside the school, but also in the community. This means that students, families, teachers, school staff, and all community members should take actions to protect themselves and others where they live, work, learn, and play. In short, success in preventing the introduction and subsequent transmission of SARS-CoV-2 in schools is connected to and dependent upon preventing transmission in communities.


Schools are an important part of the infrastructure of communities, as they provide safe, supportive learning environments for students, employ teachers and other staff, and enable parents, guardians, and caregivers to work. Schools also help to mitigate health disparities by providing critical services including school meal programs and social, physical, behavioral, and mental health services. SARS-CoV-2 transmission in schools may be a reflection of transmission in the surrounding community. Therefore, when making decisions on when to open schools for in-person learning it is important to understand SARS-CoV-2 transmission within the surrounding community to determine the possible risk of introduction and transmission of SARS-CoV-2 within the school.

International and domestic experiences have demonstrated that even when a school carefully coordinates, plans, and prepares for reopening, cases of COVID-19 may still occur. Expecting and planning for the occurrence of one or more cases of COVID-19 in schools can help respond immediately to mitigate the impact to allow the school to remain open for in-person learning, if appropriate.  When mitigation strategies are consistently and correctly used, the risk of spread within the school environment and the surrounding community is decreased.

Purpose of indicators

During the COVID-19 pandemic, States, Tribes, Localities, Territories (STLT) and school districts have been making decisions about when and how to safely open schools. Many STLTs, partners, and members of the public have asked CDC how to determine when it is safe to open schools for in-person learning.  There is no easy answer or single indicator. Many variables must be considered.

This document proposes core and secondary indicators that STLTs can use to aid in their decision-making process regarding school reopening for in-person learning. In-person learning includes all classes and activities conducted during core school hours. It does not explicitly include extracurricular activities — like sports or theater — conducted after school hours. However, these indicators could also be used to determine whether and how to implement extracurricular activities with the necessary mitigation strategies in place.

This document is meant to assist STLT officials in making decisions rather than establishing regulatory requirements. Recommendations are based on CDC’s current knowledge of COVID-19 in the United States. CDC will continue to monitor COVID-19 activity and update guidance as needed. This guidance is meant to supplement—not replace—any state, local, territorial, or tribal health and safety laws, rules, and regulations with which schools must comply.

Each STLT should decide the most appropriate indicators to reference when deciding to open, close, or reopen schools. CDC recommends the use of 3 core indicators. These core indicators include two measures of community burden (number of new cases per 100,000 persons in the past 14 days; and percentage of RT-PCR tests that are positive during the last 14 days) AND one self-assessed measure of school implementation of key mitigation strategies. CDC suggests decision-makers use one or both of the first core measures of community burden in addition to a third core indicator, the self-assessed measure of school implementation of key mitigation strategies. These key mitigation strategies should be implemented to the largest extent possible.

The two measures of community burden should be used to assess the incidence and spread of SARS-CoV-2 in the surrounding community (e.g., county) and not in the schools themselves. Currently, CDC does not recommend using these core indicators as measures of burden within the school.

Secondary indicators may also be used to complement the core indicators and further support actions taken. The list of secondary indicators is illustrative and is not meant to be exhaustive.

Other factors should also be considered in local decision-making – including the extent to which mitigation strategies are adhered to in the broader community. Local officials should seek out other sources of data to assess adherence to recommended mitigation strategies within the community. Each STLT can decide the most appropriate indicators to reference when deciding to open, close, or reopen schools.

Finally, the thresholds provided with each indicator should serve as a guide of inherent risk at the local level.

Description of indicators

The following are core and secondary indicators for decision makers to consider when deciding to open, close, or reopen schools over time. The core indicators include measures of underlying community transmission as well as a measure of adherence to key mitigation strategies.

Core indicators

Core indicators include one or both measures of community burden AND one self-assessed measure of school implementation of key mitigation strategies. Additional information including how to calculate these indicators is found in the table below.

Measures of community burden

Implementation of mitigation strategies

Schools should adopt the additional mitigation measures outlined below to the largest extent possible, practical and feasible.

Secondary indicators

Additionally, we provide secondary indicators that officials can use to support the decision-making process in local communities. These secondary indicators should not be used as the main criteria for determining the risk of disease transmission in schools. They should be used to support decision-making derived from the core indicators.

For example, knowing the percentage of hospital beds and intensive care unit beds occupied in a local hospital, including the percentage of inpatient beds occupied by a patient with COVID-19, can indicate the severity of illness in the community and whether the health care system can serve more patients. Similarly, the identification of a community outbreak indicates increased community transmission and, therefore, elevated risk of the introduction and subsequent transmission in schools.

Application and interpretation of indicators

Each indicator or combination of indicators should neither be used in isolation nor should they be viewed as hard cut-offs by STLT officials and school district decision-makers. Rather, they serve as broad guideposts of inherent risk to inform decision-making.

If, after applying the core indicators described in the table below, a school is at “medium,” “higher,” or “highest” risk of transmission, it does not mean that the school cannot re-open for in-person learning, but that the risk of introduction and subsequent transmission of SARS-CoV-2 is higher and the school could consider alternative learning models (e.g., mix of in-person and virtual learning, also known as hybrid learning, or virtual-only).

Similarly, if a school meets all core indicators and many secondary indicators, a case or cases of COVID-19 may still occur in a school among students, teachers, administrators, and other staff. As a result, falling into the category of being at “lower” or “lowest” risk of transmission does not mean that the school should relax adherence to mitigation measures.

Officials should frequently monitor these indicators and adjust accordingly.

While risk of introduction and subsequent transmission of SARS-CoV-2 in a school may be lower when indicators of community spread are lower, this risk is dependent upon the implementation of school and community mitigation strategies. If community transmission is low but school and community mitigation strategies are not implemented, then the risk of introduction and subsequent transmission of SARS-CoV-2 in a school will increase. Alternately, if community transmission is high, but school and community mitigation strategies are implemented and strictly followed as recommended, then the risk of introduction and subsequent transmission of SARS-CoV-2 in a school will decrease.

Regardless of the level of risk, as determined by the indicators, it is critical that schools use multiple mitigation strategies including consistent and correct use of masks, social distancing to the extent possible, hand hygiene and respiratory etiquette, cleaning and disinfection, and contact tracing to help prevent the spread of SARS-CoV-2.

Vigilance to mitigation strategies within schools and the broader community will reduce the risk of introduction and subsequent transmission of SARS-CoV-2 in schools. This will enable schools that are open for in-person learning to stay open and accelerate the timeline of returning to full in-person learning by schools that began the school year using hybrid or virtual learning. The application and utility of these indicators are inextricably linked to schools and communities both following recommended mitigation strategies together.

By rigorously following mitigation strategies, current and future risk of introduction and subsequent transmission of SARS-CoV-2 in schools can diminish over time regardless of baseline indicators – with risk of spread especially low when community transmission is low to begin with.

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