SARS-CoV-2 Transmission to Masked and Unmasked Close Contacts of University Students with COVID-19 - St. Louis, Missouri, January-May 2021.

Universities open for in-person instruction during the 2020-21 academic year implemented a range of prevention strategies to limit the transmission of SARS-CoV-2, the virus that causes COVID-19, including physical distancing, mask use, vaccination, contact tracing, case investigation, and quarantine protocols (1). However, in some academic programs, such as health-related programs, aviation, and kindergarten through grade 12 (K-12) education, maintaining physical distance while still providing instruction is difficult; for universities with such programs, a single confirmed case of COVID-19 could result in a large number of students, staff members, and instructors being designated close contacts and requiring quarantine if they are not fully vaccinated, even if masks were worn when contact occurred. In January 2021, the St. Louis City Health Department allowed Saint Louis University (SLU) to implement a modified quarantine protocol that considered mask use when determining which close contacts required quarantine.* To assess the impact of the protocol, SLU assessed positive SARS-CoV-2 test result rates by masking status of the persons with COVID-19 and their close contacts. During January-May 2021, 265 students received a positive SARS-CoV-2 test result; these students named 378 close contacts. Compared with close contacts whose exposure only occurred when both persons were masked (7.7%), close contacts with any unmasked exposure (32.4%) had higher adjusted odds ratios (aORs) of receiving a positive SARS-CoV-2 test result (aOR = 4.9; 95% confidence interval [CI] = 1.4-31.1). Any additional exposures were associated with a 40.0% increase in odds of a positive test result (aOR = 1.4; 95% CI = 1.2-1.6). These findings reinforce that universal masking and having fewer encounters in close contact with persons with COVID-19 prevents the spread of SARS-CoV-2 in a university setting. Universities opening for in-person instruction could consider taking mask use into account when determining which unvaccinated close contacts require quarantine if enforced testing protocols are in place. However, this study was conducted before the B.1.617.2 (Delta) variant became the dominant strain of SARS-CoV-2 in the United States, which could have affected these findings given that the Delta variant has been found to be associated with increased transmissibility compared to previous variants.

Pilot Investigation of SARS-CoV-2 Secondary Transmission in Kindergarten Through Grade 12 Schools Implementing Mitigation Strategies - St. Louis County and City of Springfield, Missouri, December 2020.

Many kindergarten through grade 12 (K-12) schools offering in-person learning have adopted strategies to limit the spread of SARS-CoV-2, the virus that causes COVID-19 (1). These measures include mandating use of face masks, physical distancing in classrooms, increasing ventilation with outdoor air, identification of close contacts,* and following CDC isolation and quarantine guidance† (2). A 2-week pilot investigation was conducted to investigate occurrences of SARS-CoV-2 secondary transmission in K-12 schools in the city of Springfield, Missouri, and in St. Louis County, Missouri, during December 7-18, 2020. Schools in both locations implemented COVID-19 mitigation strategies; however, Springfield implemented a modified quarantine policy permitting student close contacts aged ≤18 years who had school-associated contact with a person with COVID-19 and met masking requirements during their exposure to continue in-person learning.§ Participating students, teachers, and staff members with COVID-19 (37) from 22 schools and their school-based close contacts (contacts) (156) were interviewed, and contacts were offered SARS-CoV-2 testing. Among 102 school-based contacts who received testing, two (2%) had positive test results indicating probable school-based SARS-CoV-2 secondary transmission. Both contacts were in Springfield and did not meet criteria to participate in the modified quarantine. In Springfield, 42 student contacts were permitted to continue in-person learning under the modified quarantine; among the 30 who were interviewed, 21 were tested, and none received a positive test result. Despite high community transmission, SARS-CoV-2 transmission in schools implementing COVID-19 mitigation strategies was lower than that in the community. Until additional data are available, K-12 schools should continue implementing CDC-recommended mitigation measures (2) and follow CDC isolation and quarantine guidance to minimize secondary transmission in schools offering in-person learning.

Pertussis Vaccination Among Childcare Center Staff, Administrators, and Parents: Uptake, Policies, and Beliefs.

Introduction Little is known about childcare staff's and parents' uptake of and attitudes towards pertussis vaccine. Methods Questionnaires were distributed to St. Louis parents and childcare staff in fall, 2014. Parents versus staff and vaccinated versus unvaccinated individuals' beliefs regarding pertussis vaccine were compared using chi square tests. Multivariate logistic regressions were run to develop predictive models for staff's and parents' vaccine uptake. Results Overall, 351 parents and staff from 23 agencies participated (response rate = 32%). Parents were more likely than staff to have received pertussis vaccine (66.5 vs. 45.8%, X 2 = 12.5, p < .001). Predictors for staff vaccination included willingness to get vaccinated even if there was a cost (OR 6.6; CI 1.8-24.6; p < .01), awareness of vaccination recommendations (OR 5.2; CI 1.2-22.8; p < .05), and healthcare provider recommendation (OR 4.2; CI 1.2-15.1; p < .05). Parents' predictors of vaccination included perceived importance of vaccination (OR 9.9; CI 4.1-23.8; p < .001), healthcare provider recommendation (OR 4.6; CI 1.7-12.6; p < .01), believing vaccination is effective (OR 4.4; CI 1.1-18.0; p < .05), and knowing where to get vaccine (OR 3.5; CI 1.5-8.1; p < .01). Among unvaccinated staff (n = 52), 74.5% (n = 38) and 70.0% (n = 35) would receive pertussis vaccine if it were offered free of charge and onsite, respectively. Conclusions for Practice Childcare staff's and parents' pertussis vaccine uptake was higher than overall U.S. rates, though significantly lower than the Global Pertussis Initiative target. Implementing an education campaign and providing free vaccine on-site are likely to result in increased vaccine uptake.

Factors Related to Injury Prevention Programming by Missouri School Nurses.

Schools often offer injury prevention (IP) programs, but little is known about the types of programs provided or how school nurses decide which to choose. Nurses in the Missouri School Health Services Staffing Survey Database were sent a survey in spring, 2011, to describe school-based IP efforts being offered. A multivariate linear regression was conducted to delineate factors associated with offering IP programs. In total, 522 school nurses participated (33% response rate). The highest priority for selecting an IP program was perceived program effectiveness (92.3% agreement, n = 482). Determinants of offering IP programs included being asked to identify a speaker, being a high school, receiving funding in the last year, prioritizing evidence-based programs, perceiving that administrators support professional development, and knowing how to address patterns of injuries. School nurses should be competent in planning, implementing, and evaluating IP programs, and additional training may be required to accomplish this.

Missouri K-12 school collection and reporting of school-based syndromic surveillance data: a cross sectional study.

BACKGROUND: School participation in collecting and reporting syndromic surveillance (SS) data to public health officials and school nurses' attitudes regarding SS have not been assessed. METHODS: An online survey was sent to Missouri Association of School Nurses members during the 2013/2014 school year to assess whether K-12 schools were collecting and reporting SS data. Z-scores were used to assess collection versus reporting of SS indicators. Logistic regressions were used to describe factors predicting nurses' collection and reporting of SS indicators: all-cause absenteeism, influenza-like illness and gastrointestinal illness. Univariate predictors were assessed with Chi-Squares. RESULTS: In total, 133 school nurses participated (33.6 % response rate). Almost all (90.2 %, n = 120) collect at least one SS indicator; half (49.6 %, n = 66) report at least one. Schools are collecting more SS data than they are reporting to the health department (p < .05 for all comparisons). Determinants of school nurses' collection of SS data included perceived administrative support, and knowledge of collecting and analyzing SS data. The strongest predictive factors for reporting SS data were the perception that the health department was interested in SS data and being approached by the health department to collect SS data. CONCLUSION: Schools are collecting SS indicators at a relatively high rate, yet less than half of the data is reported to public health officials. Findings from this study indicate that public health officials can increase access to school-based SS data by approaching schools about collecting and reporting this important data.

Presenteeism Attitudes and Behavior Among Missouri Kindergarten to Twelfth Grade (K-12) School Nurses.

Working while ill (presenteeism) with symptoms of influenza-like illness can contribute to outbreaks, but little is known about school nurse presenteeism. Missouri Association of School Nurses members (N = 396) were sent a survey in 2013/2014. A chi square test was conducted to compare having a school culture that encourages presenteeism versus actual sick leave policies. Multivariate logistic regression was conducted to delineate factors associated with presenteeism. In total, 133 school nurses participated (33.6% response rate). Almost half (42.1%, n = 56) reported presenteeism. Nurses were more likely to feel pressure to engage in presenteeism than reported punitive sick leave policies (14.3% vs. 3.8%, χ2 = 18.3, p < .001). Presenteeism was associated with perceived pressure, odds ratio (OR) = 4.8, confidence interval (CI) = [1.5, 15.8], p < .01, and having a mild illness, OR = 3.6, CI = [1.4, 9.7], p = .01. Many school nurses engage in presenteeism, and this appears to be associated with organizational cultural norms rather than established sick leave policies.

Hospital Employee Willingness to Work during Earthquakes Versus Pandemics.

BACKGROUND: Research indicates that licensed health care workers are less willing to work during a pandemic and that the willingness of nonlicensed staff to work has had limited assessment. OBJECTIVE: We sought to assess and compare the willingness to work in all hospital workers during pandemics and earthquakes. METHODS: An online survey was distributed to Missouri hospital employees. Participants were presented with 2 disaster scenarios (pandemic influenza and earthquake); willingness, ability, and barriers to work were measured. T tests compared willingness to work during a pandemic vs. an earthquake. Multivariate linear regression analyses were conducted to describe factors associated with a higher willingness to work. RESULTS: One thousand eight hundred twenty-two employees participated (15% response rate). More willingness to work was reported for an earthquake than a pandemic (93.3% vs. 84.8%; t = 17.1; p < 0.001). Significantly fewer respondents reported the ability to work during a pandemic (83.5%; t = 17.1; p < 0.001) or an earthquake (89.8%; t = 13.3; p < 0.001) compared to their willingness to work. From multivariate linear regression, factors associated with pandemic willingness to work were as follows: 1) no children ≤3 years of age; 2) older children; 3) working full-time; 4) less concern for family; 5) less fear of job loss; and 6) vaccine availability. Earthquake willingness factors included: 1) not having children with special needs and 2) not working a different role. CONCLUSION: Improving care for dependent family members, worker protection, cross training, and job importance education may increase willingness to work during disasters.

Emergency Childcare for Hospital Workers During Disasters.

OBJECTIVES: The objectives were to determine the impact of emergency childcare (EC) needs on health care workers' ability and likelihood to work during a pandemic versus an earthquake as well as to determine the anticipated need and expected use of an on-site, hospital-provided EC program. METHODS: An online survey was distributed to all employees of an academic, urban pediatric hospital. Two disaster scenarios were presented (pandemic influenza and earthquake). Ability to work based on childcare needs, planned use of proposed hospital-provided EC, and demographics of children being brought in were obtained. RESULTS: A total of 685 employees participated (96.6% female, 79.6% white), with a 40% response rate. Those with children (n = 307) reported that childcare needs would affect their work decisions during a pandemic more than an earthquake (61.1% vs 56.0%; t = 3.7; P < 0.001). Only 28.0% (n = 80) of those who would need childcare (n = 257) report an EC plan. The scenario did not impact EC need or planned use; during scheduled versus unscheduled shifts, 40.7% versus 63.0% reported need for EC, and 50.8% versus 63.2% reported anticipated using EC. CONCLUSIONS: Hospital workers have a high anticipated use of hospital-provided EC. Provisions for EC should be an integral part of hospital disaster planning.

Infection Preventionists' Current and Preferred Training Strategies and Tools.

BACKGROUND: Educating healthcare staff on infection prevention and control (IPC) is an essential role of infection preventionists (IP), but the COVID-19 pandemic diverted resources away from IPC education. This study's purpose was to conduct an assessment of current IPC training needs. METHODS: Association for Professionals in Infection Control and Epidemiology members were invited to complete an online survey in May - June, 2023 to assess their current and preferred approaches and tools for training healthcare personnel on IPC. Vendors, retirees, APIC staff, or those not working in a healthcare setting or public health were excluded. RESULTS: In all, 2,432 IPs participated. IPs were more likely to report engaging in impromptu healthcare worker training (i.e., just-in-time teaching and team huddles) versus planned educational activities (i.e., learning modules, formal presentations, train-the-trainer, or simulation; KW=288, p <.001). IPs' top preferred teaching methodologies included simulation or interactive activity and their lowest preferred approach was independent learning modules. IPC training apps were the most frequently requested technology. DISCUSSION: IPs ranked simulation as their top preferred teaching method; however, simulation was one of the least frequently used approaches. IP education should include strategies for delivering effective impromptu training and how to develop and implement interactive simulation-based education. CONCLUSIONS: The expressed needs and preferences of IPs should be considered when developing IPC-related teaching and training tools.

Public perceptions of hospital responsibilities to those presenting without medical injury or illness during a disaster.

BACKGROUND: During natural and manmade disasters, the hospital is perceived as a central rallying and care site for the public, for both those with and without emergency medical needs. The expectations of the public may outstrip hospital plans and abilities to provide nonmedical assistance. OBJECTIVE: Our objective was to determine the public expectations of the hospital during disasters regarding resource provision. METHODS: A survey was distributed to adult patients or family members at three emergency departments (EDs). Respondents were asked to evaluate hospital responsibility to provide nine resources to those without emergency medical needs, including vaccination, medication refill or replacement, food and water, grief/stress counseling, Federal Emergency Management Agency (FEMA) access assistance, short/long-term shelter, family reunification, and hospital. Additionally, respondents answered questions regarding prior disaster experience and demographics. RESULTS: There were 961 respondents (66.9% were female, 47.5% were white, and 44.6% were black). Respondents agreed or strongly agreed that the hospital should provide the following services: event-specific vaccination (84%), medication refill/replacement (76.5%), food and water (61%), grief or stress counseling (53%), FEMA access assistance (52%), short-term shelter (51%), family reunification (50%), long-term shelter (38%), and hospital transportation (29%). Those 36-45 years of age were less likely to expect services (p < 0.05) and non-whites and those with a family member with a medical condition requiring electricity were more likely to expect services (p < 0.001 and p < 0.05, respectively). There were no differences based on frequency of ED use, sex, income, or prior disaster experience. CONCLUSION: There is a high public expectation that hospitals will provide significant nonmedical disaster relief. Understanding these expectations is essential to appropriate community disaster planning.

Disaster Preparedness in K-12 Schools: An Integrative Review.

BACKGROUND: The threat of a disaster or potential for a disaster is something that may be experienced by individuals globally. Schools are places of daily mass gatherings which make them an ideal target for mass casualty, natural disasters, and biological incidents. METHODS: An integrative review using Whittemore and Knafl's model was conducted to explore peer-reviewed publications about K-12 schools and natural disasters and pandemic preparedness and planning. RESULTS: Themes identified from the systematic review of 12 articles reflected determinants and level of school preparedness, disaster plan components, compliance with government requirements, emergency equipment, supplies, drills, and training, collaboration with outside agencies, and perceptions of school preparedness. Preparedness for disasters and biological events among schools varies and multiple factors contribute to the level of preparedness. Perceptions of school preparedness differ among school community members. Schools perceive more preparedness for disasters than their actual level. CONCLUSIONS: Our nation's schools are not adequately prepared for disasters. There is a need for further research in schools to identify and understand preparedness for disasters.

Infection preventionists' experiences during the second year of the COVID-19 pandemic: Findings from focus groups conducted with association for professionals in infection control & epidemiology (APIC) members.

INTRODUCTION: COVID-19 epidemiology changed dramatically in spring 2021 when vaccine became widely available and the Delta variant emerged. There was a need to identify current infection prevention challenges due to changing pandemic epidemiology. METHODS: Six focus groups were conducted via Zoom with APIC members in November and December, 2021 to elicit infection preventionists' (IP) experiences with the COVID-19 pandemic after the Delta variant had emerged. Each focus group was audio recorded then transcribed verbatim. Content analysis was used to identify major themes. RESULTS: In total, 90 IPs participated (average of 15 IPs per focus group). Participating IPs described multiple issues they have faced during the second year of the COVID-19 pandemic after the Delta variant emerged, including continuing challenges with personal protective equipment, changes in pandemic restrictions that caused confusion and pushback, the hope when vaccine first became available and then despair when there was more vaccine breakthrough than anticipated, staffing and medical supply shortages, overwhelming workloads, and anger towards health care personnel and IPs. However, IPs felt more valued by leadership, and reported greater internal collaboration and external coordination of care. CONCLUSIONS: The second year of the pandemic brought ongoing and new challenges for IPs, but also better coordination of care. Strategic initiatives are needed to address the identified challenges, such as how to prioritize tasks when IPs are overwhelmed.

Impacts of the COVID-19 pandemic on the infection prevention and control field: Findings from focus groups conducted with association for professionals in infection control & epidemiology (APIC) members in fall 2021.

INTRODUCTION: Emergence of the Delta variant in 2021 changed the pandemic landscape and led to healthcare surges across the US, despite availability of COVID-19 vaccine. Anecdotal information indicated that the infection prevention and control (IPC) field was changing, but formal assessment was needed. METHODS: Focus groups (6) were conducted with APIC members in November and December, 2021 to elicit infection preventionists' (IP) opinions changes to the IPC field due to the pandemic. Focus groups were audio recorded via Zoom and transcribed. Content analysis was used to identify major themes. RESULTS: Ninety IPs participated. IPs described multiple changes to the IPC field during the pandemic, including being more involved in policy development, the challenge of transitioning back to routine IPC while still responding to COVID-19, increased need for IPs across practice settings, difficulties in recruiting and retaining IPs, presenteeism in healthcare, and extensive burnout. Participants suggested approaches to improve IPs' wellbeing. CONCLUSIONS: The ongoing pandemic has brought significant changes to the IPC field, including a shortage of IPs just as the field is expanding rapidly. The continued overwhelming workload and stress due to the pandemic has resulted in burnout among IPs and the need for initiatives to improve their wellbeing.

Assessing classroom and laboratory spread of COVID-19 in a university after elimination of physical distancing.

The objective of this study was to assess COVID-19 classroom transmission in the university setting when physical distancing was eliminated. Data was collected in fall 2021 at a private university. Universal masking, robust contact tracing, vaccination requirement, and enforced testing were in place. Exposures were classified as classroom versus non-classroom. ANOVA and chi-squared tests were used to identify significant relationships between predictors and COVID-19 test result. Logistic regression was conducted to investigate the relationship between exposure type and test result. A total of 162 student cases were identified with 1,658 associated close contacts. One-third of contacts (31.1%, n = 516) only had a non-classroom exposure, 63.8% (n = 1,057) only had a classroom exposure, and 5.1% (n = 85) had both. Close contacts were significantly more likely to test positive if they had a non-classroom exposure (60 of 601; 10.0%) compared to a classroom exposure (1 of 1057; 0.1%) (OR 58.8, CI 18.5-333.3, p < 0.001). Removing physical distancing in classrooms that had universal masking did not result in high rates of COVID-19 transmission. This has policy implications because eliminating physical distancing does not greatly increase transmission risk when universal masking is in place.

Utility of child physical characteristics and verbal descriptors to aid in family reunification during disasters.

OBJECTIVE: To identify physical and verbal descriptors that have the highest concordance between parents/guardians and a research team member to improve reunification during a disaster when a child arrives at the emergency department separated from their family. METHODS: Parent and child pairs were recruited between February 2020 and March 2020. Each parent and research team member simultaneously recorded the child's physical characteristics and clothing items. Verbal children were asked personally identifying questions. An inter-rater reliability Cohen's κ determined percent agreement between each researcher and parent/child pair. RESULTS: In total, 98 parent/child pairs participated. Child's gender, eye color measured as brown versus not brown eyes, and race had the highest concordance (κ = 0.92, 0.85, and 0.84, respectively; p < .001 for all). Skin color and all hair descriptors had low concordance. All or almost all verbal children correctly identified that they have a pet and a favorite stuffed animal or blanket (100 and 98.6 percent, respectively). DISCUSSION: Only apparent age, gender, race, and general eye color (brown versus nonbrown) had strong concordance between each researcher and parent/child pair. Other descriptors such as hair color, texture, length, and detailed eye color were discordant. Additionally, several pieces of personal information, such as a pet, could expedite reunification of verbal children. CONCLUSION: Not all physical characteristics are likely to be useful in accurately identifying a child, and some personal information may aid in reunification. Using the most concordant information should allow for more accurate and rapid reunification of children and their caregivers during disasters.

Non-Pediatric Nurses' Willingness to Provide Care to Pediatric Patients during a Disaster: An Assessment of Pediatric Surge Capacity in Four Midwestern Hospitals.

OBJECTIVE: To assess non-pediatric nurses' willingness to provide care to pediatric patients during a mass casualty event (MCE). METHODS: Nurses from 4 non-pediatric hospitals in a major metropolitan Midwestern region were surveyed in the fall of 2018. Participants were asked about their willingness to provide MCE pediatric care. Hierarchical logistical regression was used to describe factors associated with nurses' willingness to provide MCE pediatric care. RESULTS: In total, 313 nurses were approached and 289 completed a survey (response rate = 92%). A quarter (25.3%, n = 73) would be willing to provide MCE care to a child of any age; 12% (n = 35) would provide care only to newborns in the labor and delivery area, and 16.6% (n = 48) would only provide care to adults. Predictors of willingness to provide care to a patient of any age during an MCE included providing care to the youngest-age children during routine duties, reporting confidence in calculating doses and administering pediatric medications, working in the emergency department, being currently or previously certified in PALS, and having access to pediatric-sized equipment in the unit or hospital. CONCLUSION: Pediatric surge capacity is lacking among nurses. Increasing nurses' pediatric care self-efficacy could improve pediatric surge capacity and minimize morbidity and mortality during MCEs.

Computational modeling of first responders' willingness to accept radiation exposure during radiological or nuclear events.

Since the events of 9/11, a concerted interagency effort has been undertaken to create comprehensive emergency planning and preparedness strategies for the management of a radiological or nuclear event in the US. These planning guides include protective action guidelines, medical countermeasure recommendations, and systems for diagnosing and triaging radiation injury. Yet, key areas such as perception of risk from radiation exposure by first responders have not been addressed. In this study, we identify the need to model and develop new strategies for medical management of large-scale population exposures to radiation and examine the phenomena of radiation dread and its role in emergency response using an agent-based modeling approach. Using the computational modeling platform NetLogo, we developed a series of models examining factors affecting first responders' willingness to work (WTW) in the context of entering areas where radioactive contamination is present or triaging individuals potentially contaminated with radioactive materials. In these models, the presence of radiation subject matter experts (SMEs) was found to increase WTW. Degree of communication was found to be a dynamic variable with either positive or negative effects on WTW dependent on the initial WTW demographics of the test population. Our findings illustrate that radiation dread is a significant confounder for emergency response to radiological or nuclear events and that increasing the presence of radiation SME in the field and communication among first responders when such radiation SMEs are present will help mitigate the effect of radiation dread and improve first responder WTW during future radiological or nuclear events.

Challenges in managing, sustaining, and assessing closed point of dispensing sites: Findings from a qualitative study.

Most U.S. public health agencies rely upon closed points of dispensing (PODs) to aid in medical countermeasure (MCM) distribution. However, few studies have focused on how to assess closed POD preparedness and none have examined best practices for managing sites once they have been recruited. This study involved qualitative interviews with U.S. disaster planners to elucidate their approaches and challenges to managing, sustaining, and assessing existing closed POD sites. In all, 16 disaster planners participated. Common management practices included frequent communication with sites, providing formal and informal training, and assisting with POD exercises. Very few jurisdictions reported doing formal assessments of closed POD sites. The largest challenges identified were staff turnover and keeping sites engaged, sometimes leading to sites voluntarily withdrawing or needing to be removed from being a closed POD. Frequent communication and building partnerships with closed POD site personnel were recommended to maintain and sustain existing sites. Formal and informal assessments will provide assurance of deployment readiness. Closed POD management is a challenging, but essential process to ensure readiness to deploy. Practices outlined by this study can be implemented to enhance closed POD network management at other jurisdictions. This should increase the ability to distribute MCMs rapidly during a future event, contributing to stronger community resilience. Public health officials should continue expanding and improving closed POD networks to enable MCM delivery and minimize morbidity and mortality related to mass casualty events.

Modifications to student quarantine policies in K-12 schools implementing multiple COVID-19 prevention strategies restores in-person education without increasing SARS-CoV-2 transmission risk, January-March 2021.

OBJECTIVE: To determine whether modified K-12 student quarantine policies that allow some students to continue in-person education during their quarantine period increase schoolwide SARS-CoV-2 transmission risk following the increase in cases in winter 2020-2021. METHODS: We conducted a prospective cohort study of COVID-19 cases and close contacts among students and staff (n = 65,621) in 103 Missouri public schools. Participants were offered free, saliva-based RT-PCR testing. The projected number of school-based transmission events among untested close contacts was extrapolated from the percentage of events detected among tested asymptomatic close contacts and summed with the number of detected events for a projected total. An adjusted Cox regression model compared hazard rates of school-based SARS-CoV-2 infections between schools with a modified versus standard quarantine policy. RESULTS: From January-March 2021, a projected 23 (1%) school-based transmission events occurred among 1,636 school close contacts. There was no difference in the adjusted hazard rates of school-based SARS-CoV-2 infections between schools with a modified versus standard quarantine policy (hazard ratio = 1.00; 95% confidence interval: 0.97-1.03). DISCUSSION: School-based SARS-CoV-2 transmission was rare in 103 K-12 schools implementing multiple COVID-19 prevention strategies. Modified student quarantine policies were not associated with increased school incidence of COVID-19. Modifications to student quarantine policies may be a useful strategy for K-12 schools to safely reduce disruptions to in-person education during times of increased COVID-19 community incidence.