Introduction

Before the massive COVID-19 vaccination campaign for school children, school closure was the most adopted nonpharmaceutical policy to prevent cluster transmission in schools and subsequently household transmission. However, the effectiveness of school closure is not consistent among studies conducted in different countries []. With the adaptation of SARS-CoV-2 to humans, the highly attacked population has shifted from elderly people and adults to school children []. As epidemiological characteristics change, the evaluation of the school closure policy may be different. One study conducted during the early phase of the pandemic in 2020 [] examined the effect of policies, including school closure, on reducing local transmission of COVID-19. At that time, the majority of the infected population was adults. Therefore, the effectiveness of school closure was not significant. However, as the pandemic progressed, the low vaccination coverage of school children and the reopening of schools [] caused the infection rate among school children to surge. In the United States, children aged <18 years accounted for 17.3% of reported cases of COVID-19 until August 30, 2022 []. In Taiwan, up to calendar week 31 in 2022, the proportion of confirmed cases of COVID-19 among those aged under 20 years was 13.9% []. The attack rate and susceptibility to COVID-19 infection are lower in children than in adults according to current evidence []. Current research suggests that COVID-19 angiotensin-converting enzyme 2 receptors are scarce in the respiratory tract of children, leading to fewer receptors for viruses to bind to []. Although there appear to be few confirmed cases among children, some data suggest that children are more likely to be asymptomatic or mild and that they are not initially tested, which leads to underreported cases []. Children may still be a source of infection transmission [].

The prevention of infection and severe complications, especially in children, remains a public health issue. Nonpharmaceutical interventions (NPIs) are effective strategies to mitigate the spread of epidemics in the community. Strategies include maintaining personal hygiene, wearing masks, social distancing, daily temperature measurements, and symptom monitoring. School closure or class suspension as an NPI is often considered an option for suppressing the spread of influenza and enterovirus epidemics [-]. School closure can reduce transmission first among children and then in the community []. A published systematic review noted that the mean reduction in the peak of the influenza epidemic was 29.65% (SD 23.63) after implementing school closure []. The earlier implementation of school closure is more likely to reduce and delay the peak of the influenza epidemic []. School closure can decrease the number of daily contacts between schoolmates in close proximity. A simulation study showed that reproduction number and age-specific susceptibility to infection influenced the policy effect of school closure []. School closure is less effective under the condition of a larger reproduction number (>1.8) and a population with less susceptibility to infection []. Greater transmissibility (reproduction number) and lower susceptibility to COVID-19 in children are opposed to influenza. The effects of school closure to combat COVID-19 at different times and in different countries are still disputed [].

A recent systematic review revealed that the impact of school closure on COVID-19 is smaller than that of other social distancing interventions, and school closure alone only prevents 2%-4% of deaths []. In the fall of 2020 in Croatia, an association was found between school closure and COVID-19 morbidity and mortality, while in the winter of 2021, the association was insignificant []. According to a United Nations International Children’s Emergency Fund (UNICEF) report, from March 2020 to February 2021, schools for more than 168 million children worldwide were closed for nearly a year []. During the COVID-19 pandemic, school closure policies have been widely implemented worldwide to reduce exposure rates and transmission risks ahead of mass vaccination. According to a systematic review of school closure during the pandemic, school closure and in-school mitigation measures were associated with reduced COVID-19 transmission in the community []. However, they also noted that assessing the impact of school closure is challenging because many nonpharmacological interventions are being implemented simultaneously, and the potential negative impacts on students’ mental and physical health were also widely discussed [,]. School closure can negatively influence children’s physical and mental health, and education, and can have an economic impact on working parents. Therefore, before deciding on the implementation of school closure, we must consider its effects and costs. The timing of the intervention to mitigate emerging infectious diseases was referenced by prompt surveillance. Sentinel-based surveillance for monitoring disease activity has been widely used in different countries. Sentinel surveillance can detect early aberrations in the daily incidence of a disease or the outpatient consultation rate []. In this study, we built community-based syndromic surveillance (ie, Sentinel Plus) in sentinel clinics and community hospitals since June 2018 in Taipei City, Taiwan. The advantages of Sentinel Plus can be used to monitor a variety of syndromes and detect changes across 7 age groups and health care facility levels, including community hospitals and clinics []. Sentinel Plus is designed for daily automated symptom monitoring of 34 current symptom groups in an outpatient setting to complement emergency room surveillance. In our previous study [], Sentinel Plus performed better than other surveillance systems in early aberration detection in influenza-like illnesses and enterovirus-like syndromes. Owing to the lack of empirical evidence on the influence of the COVID-19 epidemic during the implementation of school closure, this study aimed to explore the association between school closure and the standardized incidence of COVID-19–related syndromes derived from daily outpatient syndromic surveillance data. Furthermore, we elucidated the association between 7 different age stratifications and the hierarchy of medical facilities. Moreover, the effects of school closure were explored in different extents of mobility changes between 2021 and 2022.

MethodsData Source

We collected specific syndromic groups daily from a community-based enhanced sentinel surveillance system named “Sentinel Plus,” which has been designed for the early detection of aberrations of epidemics in clinics and community hospitals since June 2018 []. After November 2020, Sentinel Plus monitors expanded the syndromic groups from 23 to 34 syndromes owing to the COVID-19 pandemic. The specific International Classification of Diseases, 10th Revision (ICD-10) diagnoses from the hospital information systems of participating clinics and community hospitals were computed on-site and aggregated into 34 syndromic groups and 7 age groups without any patient identifiers. The aggregated data were then sent to Sentinel Plus through a secure channel.

In this study, we used COVID-19–related syndromes from Sentinel Plus. ICD-10 diagnoses of daily visits from December 2020 to June 2022 were obtained from 130 participating clinics, 12 health centers, and 8 community hospitals in Taipei City. The definition of COVID-19–related syndromes was discussed with the family physician and infectious disease physician, and was therefore identified by ICD-10 codes, including R05, R06.02, R50.9, R43.0, R43.1, R43.2, R43.8, R43.9, R19.7, J06.9, J12.89, J34.89, R07.0, R51, and R19.7. Although the confirmed diagnosis of COVID-19 was implemented in the system in November 2020, reimbursement for the diagnosis of COVID-19 through the routine national health insurance system began at the end of May 2021. From June 2021 to late May 2022, COVID-19 testing by polymerase chain reaction (PCR) was only implemented in designated hospitals and community screening stations. Clinics did not make a diagnosis of COVID-19 but transferred possible patients to hospitals and screening stations during that time. Therefore, we did not use a COVID-19–confirmed diagnosis as the primary outcome.

In addition to the surveillance data, we also incorporated the policy of school closure in Taipei City and the Google COVID-19 Community Mobility Report for analysis. School closure information was obtained from a press release from the Department of Education of Taipei City Government. Daily percentage changes in people’s visits to and staying time in the 6 categories of places were obtained from the COVID-19 Community Mobility Report []. The data charted movement trends over time compared to baseline days, which was the median value for the corresponding day of the week during the 5-week period from January 3 to February 6, 2020. Categories for grouping places with similar characteristics for social distancing guidance included grocery stores and pharmacies, parks, transit stations, retail and recreation, residences, and workplaces. Daily alert levels for COVID-19 from the Central Epidemic Command Center were downloaded from the Taiwan Centers for Disease Control (CDC) [] as a reference. In Sentinel Plus, the age group was classified into 7 categories as follows: 0-6, 7-12, 13-18, 19-24, 25-44, 45-64, and ≥65 years.

Ethics Approval

The study was approved by the Institutional Review Board of the Biomedical Science Research, Academia Sinica (AS-IRB-BM-18017).

Data Analysis

In Taipei City, school closure and distance learning at home were implemented from May 18, 2021, to July 2, 2021. The time intervals from January 1, 2021, to June 1, 2021 (T1-1) and June 15, 2021 (T1-2) were analyzed. In 2022, Taipei’s school closure was from May 23 to June 5. The time intervals from January 1, 2022, to June 6, 2022 (T2-1) and June 20, 2022 (T2-2) were analyzed. We assumed that the school closure on COVID-19–related syndromes lasted 1-14 days, 2-15 days, or 3-16 days after the intervention. We explored the effect of school closure on the standardized incidence of COVID-19–related syndromes, which were derived from Sentinel Plus by autoregressive integrated moving average interrupted time series-distributed lag (ARIMAITS-DL) [], and quantified the influence of different age groups and the hierarchy of medical facilities, such as clinics and community hospitals. Moreover, the effects of school closure under movement changes between 2021 and 2022 were explored. Incidence was defined as the daily counts for the diagnosis of COVID-19–related syndromes divided by the total daily outpatient visits multiplied by 1000. Patients may be diagnosed with multiple ICD codes in the same syndromic group, and thus, the incidence may be >1000. Owing to the low number of outpatient visits on weekends and holidays, we removed daily visits below 200 from our analysis and in our plot. The ARIMAITS-DL model with exogenous variables simultaneously models both the unclear intervention time and the distributed effect of the intervention over time. It is assumed that the intervention effect is uniformly distributed over time. We checked the collinearity between the 6 categories of grouping places from the Google Community Mobility Report and deleted categories, including retail, recreation, and transit stations, owing to a variance inflation factor >10. Parks were also excluded because parks usually refer to official national parks and not the general outdoors. Workplaces were excluded because children and retirees rarely go there. Exogenous variables were grocery stores, pharmacies, and residences. The regression parameters were estimated using the maximum likelihood method. The appropriate autoregressive integrated moving average (ARIMA) parameters (p,d,q) were selected using the Akaike information criterion (AIC) and model fitting with different age groups and hierarchies of medical facilities. We checked the sensitivity of the results by changing the duration of the school closure effect with model-fitting statistics using the AIC. Finally, the residuals of the selected model and autocorrelation were tested using a residual plot and the Ljung-Box test, respectively. If autocorrelation still existed in the residuals, different autoregressive or moving average orders were chosen. All analyses were performed using R software (version 4.2.1) [], including the forecast [] and ggplot2 [] packages.

Results

In the first observation period of 2021 (T1-1 and T1-2), the alert level of COVID-19 was elevated to Level 3 on May 19, 2021. In the second observation period in the first half of 2022 (T2-1 and T2-2), the alert level of COVID-19 was Level 2 (). The standardized incidence of the diagnosis of COVID-19–related syndromes separately from clinics and community hospitals in the observed period is illustrated in . The epi-curve varied regularly on workdays and weekends, and the trend has been decreasing since school closure, particularly in clinics, in 2021.

The upper panel represents data from clinics, and the lower panel represents data from community hospitals. The color of the first row represents 3 different alert levels in Taipei City issued by the Central Epidemic Command Center (CECC) of Taiwan. Blue represents Level 1, green represents Level 2, and red represents Level 3.

The epi-curves marked between the 2 red dashed lines are the periods of school closure. Daily visits below 200 (weekends and spring festivals) were removed from the plot. Removed dates in clinics: February 12, 2021; February 01, 2022; and February 02, 2022. Removed dates in community hospitals: December 20, 2020; February 14, 2021; July 25, 2021; September 26, 2021; October 11, 2021; November 21, 2021; December 05, 2021; December 12, 2021; January 09, 2022; and February 13, 2022.

The median incidence of COVID-19–related syndromes was higher in clinics than in community hospitals in 2021 and 2022 ( and , respectively). Before the implementation of school closure, the median incidence of COVID-19–related syndromes was higher in 2021 than in 2022 in both clinics and community hospitals. In different age groups, the incidence of patients aged <18 years was relatively high in clinics. In contrast, in community hospitals, the incidence of patients aged over 25 years was relatively high in 2021 and 2022.

In the study time interval of 2021 (T1-1), the overall standardized incidence of COVID-19–related syndromes was not significantly associated with the intervention of school closure in clinics (coefficient −0.84, 95% CI −1.69 to 0.01), but was negatively associated in community hospitals (coefficient −1.24, 95% CI −2.40 to −0.08) ().

In different age groups, school closure had a significant negative association with the standardized incidence among people aged 13-18 years and ≥65 years in clinics. School closure had a significant positive association with the standardized incidence among people aged 19-24 years in community hospitals. Furthermore, the standardized incidence had significant positive associations with the change in movement toward grocery and pharmacy stores among people aged 7-12 years and 25-44 years in clinics. Furthermore, changes in movement toward residences were significantly positively associated with standardized incidence rates in all age groups, in the 13-18 and >25 age groups in clinics, and in all age groups in community hospitals. However, changes in movement toward residences were significantly negatively associated with the standardized incidence among people aged 7-18 years in community hospitals.

In the study time interval of 2021 (T1-2), the overall standardized incidence of COVID-19–related syndromes in both clinics and community hospitals was not significantly associated with the school closure intervention (clinic: coefficient −0.42, 95% CI −1.34 to 0.50; community hospital: coefficient −0.45, 95% CI −1.65 to 0.76) (). In different age groups, school closure was significantly negatively associated with the standardized incidence among people aged 0-6, 13-18, and ≥65 years in clinics. However, school closure had a significant positive association with the standardized incidence among people aged 19-24 years in community hospitals.

In the first half of 2022 (T2-1), school closure had no relationship with the overall standardized incidence in both clinics and community hospitals (clinic: coefficient −0.40, 95% CI −0.90 to 0.10; community hospital: coefficient −0.29, 95% CI −0.60 to 0.03) (). In the 45-64 and ≥65 age groups in clinics, school closure had a significant negative association with the standardized incidence. In the 0-6, 7-12, and 19-24 age groups in community hospitals, school closure had a significant negative association with the standardized incidence. Among people of all ages and those aged >25 years in clinics and people of all ages and those aged >45 years in community hospitals, changes in movement toward grocery and pharmacy stores were positively associated with the standardized incidence. In clinics, among people of all ages and those aged >19 years, movement changes toward residences had a significantly positive association with the standardized incidence. In community hospitals, among people of all ages and those aged 0-6, 7-12, 19-24, and >45 years, movement changes toward residences had a significantly positive association with the standardized incidence.

In the first half of 2022 (T2-2), school closure had no relation with the overall standardized incidence in both clinics and community hospitals (clinic: coefficient −0.29, 95% CI −0.77 to 0.19; community hospital: coefficient −0.19, 95% CI −0.48 to 0.10) (). In the 45-64 and ≥65 age groups in clinics, school closure had a significant negative association with the standardized incidence.

In 2021, during a small-scale epidemic with a soft lockdown policy in effect from May to July, school closure effectively reduced the COVID-19 incidence among preschool students, junior and senior high school students, and elders. During both time intervals, there was an increase in mobility to residences, grocery stores, and pharmacies based on the Google Community Report [].

‎Figure 1. Time series plot of COVID-19–related syndromes in Taipei City. Table 1. Comparison of the daily incidence of the diagnosis of COVID-19–related syndromes before and after school closure between clinics and community hospitals in 2021.AgeBefore school closure in 2021Two weeks after school closure in 2021Four weeks after school closure in 2021
Clinic, median (IQR)Hospital, median (IQR)Clinic, median (IQR)Hospital, median (IQR)Clinic, median (IQR)Hospital, median (IQR)Overall59.88 (19.22)1.78 (0.47)64.93 (12.35)3.46 (0.97)54.10 (22.89)2.53 (1.71)0-6 years108.67 (18.29)0.49 (0.29)108.36 (21.32)0.23 (0.45)98.40 (26.99)0.00 (0.24)7-12 years126.15 (25.89)0.34 (0.31)127.85 (29.46)0.00 (0.31)127.85 (22.71)0.00 (0.06)13-18 years101.23 (32.37)0.25 (0.55)108.70 (48.43)0.00 (0.47)94.59 (39.02)0.00 (0.06)19-24 years85.14 (19.58)0.59 (0.49)99.34 (42.19)1.61 (2.06)77.27 (59.28)1.01 (1.69)25-44 years71.04 (14.90)2.83 (1.09)74.96 (21.83)7.05 (2.17)67.29 (38.91)6.14 (3.20)45-64 years42.01 (16.98)3.54 (1.47)50.84 (7.48)6.55 (1.11)48.01 (17.37)5.86 (3.84)≥65 years36.90 (20.91)4.16 (1.79)48.07 (11.50)6.57 (2.93)46.62 (13.66)5.05 (3.89)Table 2. Comparison of the daily incidence of the diagnosis of COVID-19–related syndromes before and after school closure between clinics and community hospitals in 2022.AgeBefore school closure in 2022Two weeks after school closure in 2022Four weeks after school closure in 2022
Clinic, median (IQR)Hospital, median (IQR)Clinic, median (IQR)Hospital, median (IQR)Clinic, median (IQR)Hospital, median (IQR)Overall46.82 (18.10)2.24 (1.91)46.20 (10.97)2.10 (0.55)43.16 (7.01)1.99 (0.34)0-6 years117.46 (17.09)0.42 (0.27)90.98 (45.42)0.25 (0.38)85.54 (17.40)0.37 (0.26)7-12 years117.05 (30.00)0.22 (0.29)78.59 (52.81)0.66 (0.25)83.12 (48.34)0.42 (0.30)13-18 years85.41 (40.21)0.27 (0.58)30.56 (68.81)0.75 (0.44)38.22 (42.48)0.49 (0.50)19-24 years51.65 (32.97)0.39 (0.66)50.36 (24.44)0.42 (0.32)48.75 (8.29)0.42 (0.33)25-44 years50.68 (16.11)3.07 (1.36)59.42 (15.25)4.16 (1.71)54.02 (11.25)4.16 (1.72)45-64 years31.49 (20.66)3.17 (2.19)49.00 (10.89)3.75 (1.55)39.27 (11.46)3.92 (1.25)≥65 years32.10 (21.02)3.48 (1.61)40.48 (11.62)4.37 (0.64)35.34 (7.12)4.37 (0.89)Table 3. Effect of school closure on the standardized incidence of COVID-19–related syndromes in clinics and community hospitals from January 1, 2021, to June 1, 2021.Age and variableClinic (estimation), coefficient (95% CI)Hospital (estimation), coefficient (95% CI)Overall


ARIMAa (p,d,q)ARIMA (9,0,0)ARIMA (3,0,0)
School closure−0.84 (−1.69 to 0.01)−1.24 (−2.40 to −0.08)b
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.03)−0.01 (−0.04 to 0.01)
Residential percent change from baseline0.10 (0.06 to 0.14)b0.22 (0.16 to 0.27)b0-6 years


ARIMA (p,d,q)ARIMA (7,0,0)ARIMA (7,0,1)
School closure−0.01 (−1.00 to 0.97)−0.19 (−1.06 to 0.68)
Grocery and pharmacy percent change from baseline0.02 (−0.004 to 0.04)0.01 (−0.01 to 0.03)
Residential percent change from baseline0.04 (−0.004 to 0.09)−0.04 (−0.08 to 0.001)7-12 years


ARIMA (p,d,q)ARIMA (2,0,8)ARIMA (2,0,7)
School closure−0.08 (−1.30 to 1.14)0.81 (−0.27 to 1.88)
Grocery and pharmacy percent change from baseline0.03 (0.002 to 0.06)b0.02 (−0.001 to 0.05)
Residential percent change from baseline0.003 (−0.05 to 0.06)−0.12 (−0.17 to −0.07)b13-18 years


ARIMA (p,d,q)ARIMA (0,1,1)ARIMA (0,0,0)
School closure−1.58 (−2.90 to −0.26)b0.56 (−0.70 to 1.83)
Grocery and pharmacy percent change from baseline−0.02 (−0.05 to 0.01)0.03 (−0.004 to 0.05)
Residential percent change from baseline0.07 (0.01 to 0.12)b−0.09 (−0.16 to −0.03)b19-24 years


ARIMA (p,d,q)ARIMA (1,0,0)ARIMA (5,0,0)
School closure0.99 (−0.31 to 2.29)2.49 (1.63 to 3.34)b
Grocery and pharmacy percent change from baseline0.02 (−0.01 to 0.05)0.001 (−0.02 to 0.02)
Residential percent change from baseline0.03 (−0.02 to 0.08)−0.003 (−0.05 to 0.04)25-44 years


ARIMA (p,d,q)ARIMA (0,1,7)ARIMA (0,0,1)
School closure0.65 (−0.52 to 1.83)0.14 (−0.99 to 1.27)
Grocery and pharmacy percent change from baseline0.05 (0.02 to 0.08)b−0.02 (−0.04 to 0.01)
Residential percent change from baseline0.05 (0.001 to 0.09)b0.01 (−0.04 to 0.06)45-64 years


ARIMA (p,d,q)ARIMA (6,1,2)ARIMA (1,0,3)
School closure−0.17 (−1.17 to 0.82)0.96 (−0.22 to 2.15)
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.04)0.01 (−0.02 to 0.03)
Residential percent change from baseline0.10 (0.06 to 0.14)b0.06 (−0.0001 to 0.11)≥65 years


ARIMA (p,d,q)ARIMA (8,0,0)ARIMA (0,0,0)
School closure−1.30 (−2.06 to −0.55)b0.68 (−0.58 to 1.93)
Grocery and pharmacy percent change from baseline−0.002 (−0.02 to 0.01)−0.02 (−0.05 to 0.01)
Residential percent change from baseline0.15 (0.12 to 0.19)b0.06 (−0.004 to 0.12)

aARIMA: autoregressive integrated moving average.

bP<.05.

Table 4. Effect of school closure on the standardized incidence of COVID-19–related syndromes in clinics and community hospitals from January 1, 2021, to June 15, 2021.Age and variableClinic (estimation), coefficient (95% CI)Hospital (estimation), coefficient (95% CI)Overall


ARIMAa (p,d,q)ARIMA (6,1,2)ARIMA (1,0,2)
School closure−0.42 (−1.34 to 0.50)−0.45 (−1.65 to 0.76)
Grocery and pharmacy percent change from baseline0.03 (0.01 to 0.06)b−0.01 (−0.04 to 0.01)
Residential percent change from baseline0.08 (0.05 to 0.12)b0.05 (−0.02 to 0.11)0-6 years


ARIMA (p,d,q)ARIMA (9,0,0)ARIMA (7,0,1)
School closure−0.90 (−1.73 to −0.06)b−0.43 (−1.14 to 0.27)
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.03)0.01 (−0.01 to 0.03)
Residential percent change from baseline0.03 (−0.01 to 0.07)−0.04 (−0.07 to 0.00)7-12 years


ARIMA (p,d,q)ARIMA (2,0,8)ARIMA (0,0,6)
School closure−0.05 (−1.00 to 0.90)0.61 (−0.30 to 1.52)
Grocery and pharmacy percent change from baseline0.02 (−0.01 to 0.05)0.01 (−0.02 to 0.04)
Residential percent change from baseline0.01 (−0.03 to 0.06)−0.10 (−0.14 to −0.05)b13-18 years


ARIMA (p,d,q)ARIMA (2,0,6)ARIMA (0,0,0)
School closure−1.43 (−2.43 to −0.43)b0.42 (−0.59 to 1.43)
Grocery and pharmacy percent change from baseline0.02 (−0.01 to 0.05)0.02 (−0.01 to 0.05)
Residential percent change from baseline0.05 (0.005 to 0.10)b−0.07 (−0.12 to −0.02)b19-24 years


ARIMA (p,d,q)ARIMA (1,0,0)ARIMA (5,0,0)
School closure−0.39 (−1.37 to 0.59)1.44 (0.45 to 2.42)b
Grocery and pharmacy percent change from baseline0.03 (0.005 to 0.06)b0.01 (−0.01 to 0.04)
Residential percent change from baseline0.01 (−0.04 to 0.05)−0.04 (−0.09 to 0.005)25-44 years


ARIMA (p,d,q)ARIMA (0,1,10)ARIMA (0,0,1)
School closure−0.21 (−1.47 to 1.05)0.10 (−0.77 to 0.97)
Grocery and pharmacy percent change from baseline0.05 (0.03 to 0.08)b−0.02 (−0.04 to 0.01)
Residential percent change from baseline0.01 (−0.02 to 0.05)0.00 (−0.04 to 0.04)45-64 years


ARIMA (p,d,q)ARIMA (6,1,2)ARIMA (5,0,0)
School closure−0.01 (−1.13 to 1.11)0.26 (−0.67 to 1.18)
Grocery and pharmacy percent change from baseline0.03 (0.01 to 0.06)b0.02 (−0.01 to 0.04)
Residential percent change from baseline0.07 (0.03 to 0.12)b0.02 (−0.03 to 0.06)≥65 years


ARIMA (p,d,q)ARIMA (7,0,0)ARIMA (0,0,0)
School closure−1.29 (−2.47 to −0.11)b−0.21 (−1.24 to 0.83)
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.03)0.00 (−0.03 to 0.03)
Residential percent change from baseline0.12 (0.09 to 0.14)b0.02 (−0.03 to 0.07)

aARIMA: autoregressive integrated moving average.

bP<.05.

Table 5. Effect of school closure on the standardized incidence of COVID-19–related syndromes in clinics and community hospitals from January 1, 2022, to June 6, 2022.Age and variableClinic (estimation), coefficient (95% CI)Hospital (estimation), coefficient (95% CI)Overall


ARIMAa (p,d,q)ARIMA (8,0,0)ARIMA (2,0,2)
School closure−0.40 (−0.90 to 0.10)−0.29 (−0.60 to 0.03)
Grocery and pharmacy percent change from baseline0.03 (0.01 to 0.05)b0.04 (0.02 to 0.06)b
Residential percent change from baseline0.09 (0.04 to 0.14)b0.14 (0.09 to 0.18)b0-6 years


ARIMA (p,d,q)ARIMA (0,0,3)ARIMA (5,0,0)
School closure−0.23 (−0.63 to 0.18)−0.09 (−0.18 to −0.01)b
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.03)−0.01 (−0.01 to 0.000003)
Residential percent change from baseline0.03 (−0.001 to 0.07)0.03 (0.02 to 0.04)b7-12 years


ARIMA (p,d,q)ARIMA (5,0,2)ARIMA (6,0,2)
School closure−0.05 (−0.54 to 0.45)−0.25 (−0.50 to −0.01)b
Grocery and pharmacy percent change from baseline0.00 (−0.02 to 0.02)0.00 (−0.02 to 0.01)
Residential percent change from baseline0.04 (−0.002 to 0.08)0.07 (0.03 to 0.10)b13-18 years


ARIMA (p,d,q)ARIMA (0,1,9)ARIMA (10,0,0)
School closure−0.35 (−0.74 to 0.04)−0.05 (−0.32 to 0.23)
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.03)0.01 (−0.01 to 0.02)
Residential percent change from baseline−0.01 (−0.06 to 0.04)0.02 (−0.02 to 0.05)19-24 years


ARIMA (p,d,q)ARIMA (6,0,2)ARIMA (7,0,0)
School closure−0.31 (−0.80 to 0.17)−0.38 (−0.74 to −0.03)b
Grocery and pharmacy percent change from baseline−0.01 (−0.03 to 0.01)−0.01 (−0.03 to 0.02)
Residential percent change from baseline0.06 (0.02 to 0.10)b0.09 (0.03 to 0.15)b25-44 years


ARIMA (p,d,q)ARIMA (3,0,5)ARIMA (7,0,0)
School closure−0.23 (−0.68 to 0.22)0.06 (−0.28 to 0.41)
Grocery and pharmacy percent change from baseline0.02 (0.001 to 0.04)b−0.01 (−0.03 to 0.01)
Residential percent change from baseline0.07 (0.03 to 0.11)b0.02 (−0.03 to 0.06)45-64 years


ARIMA (p,d,q)ARIMA (6,1,0)ARIMA (0,0,1)
School closure−0.46 (−0.77 to −0.15)b−0.22 (−0.48 to 0.05)
Grocery and pharmacy percent change from baseline0.04 (0.02 to 0.05)b0.04 (0.02 to 0.06)b
Residential percent change from baseline0.10 (0.06 to 0.14)b0.10 (0.06 to 0.13)b≥65 years


ARIMA (p,d,q)ARIMA (7,0,0)ARIMA (0,0,4)
School closure−0.42 (−0.73 to −0.12)b0.02 (−0.33 to 0.36)
Grocery and pharmacy percent change from baseline0.04 (0.02 to 0.05)b0.04 (0.01 to 0.06)b
Residential percent change from baseline0.10 (0.06 to 0.14)b0.08 (0.04 to 0.12)b

aARIMA: autoregressive integrated moving average.

bP<.05.

Table 6. Effect of school closure on the standardized incidence of COVID-19–related syndromes in clinics and community hospitals from January 1, 2022, to June 20, 2022.Age and variableClinic (estimation), coefficient (95% CI)Hospital (estimation), coefficient (95% CI)Overall


ARIMAa (p,d,q)ARIMA (8,0,0)ARIMA (0,0,8)
School closure−0.29 (−0.77 to 0.19)−0.19 (−0.48 to 0.10)
Grocery and pharmacy percent change from baseline0.03 (0.02 to 0.05)b0.04 (0.02 to 0.06)b
Residential percent change from baseline0.09 (0.04 to 0.14)b0.13 (0.09 to 0.17)b0-6 years


ARIMA (p,d,q)ARIMA (7,0,0)ARIMA (10,0,0)
School closure−0.08 (−0.51 to 0.35)−0.05 (−0.20 to 0.09)
Grocery and pharmacy percent change from baseline0.00 (−0.01 to 0.02)−0.01 (−0.02 to 0.00)
Residential percent change from baseline0.05 (0.01 to 0.10)b0.02 (0.01 to 0.04)b7-12 years


ARIMA (p,d,q)ARIMA (7,0,0)ARIMA (8,0,2)
School closure0.05 (−0.39 to 0.48)−0.29 (−0.61 to 0.04)
Grocery and pharmacy percent change from baseline−0.01 (−0.02 to 0.01)0.003 (−0.01 to 0.02)
Residential percent change from baseline0.04 (0.001 to 0.08)b0.02 (−0.01 to 0.06)13-18 years


ARIMA (p,d,q)ARIMA (2,0,1)ARIMA (10,0,0)
School closure−0.26 (−0.70 to 0.19)−0.02 (−0.31 to 0.26)
Grocery and pharmacy percent change from baseline0.01 (−0.01 to 0.03)0.01 (−0.01 to 0.02)
Residential percent change from baseline0.00 (−0.04 to 0.04)0.01 (−0.02 to 0.05)19-24 years


ARIMA (p,d,q)ARIMA (3,0,3)ARIMA (7,0,0)
School closure−0.31 (−0.74 to 0.13)−0.30 (−0.68 to 0.08)
Grocery and pharmacy percent change from baseline−0.01 (−0.03 to 0.01)−0.01 (−0.03 to 0.01)
Residential percent change from baseline0.06 (0.03 to 0.10)b0.03 (−0.01 to 0.08)25-44 years


ARIMA (p,d,q)ARIMA (5,0,3)ARIMA (7,0,0)
School closure−0.17 (−0.61 to 0.28)0.10 (−0.23 to 0.44)
Grocery and pharmacy percent change from baseline0.02 (0.001 to 0.04)b