## Abstract

Understanding the effectiveness of a school closure in limiting social interaction and the economic impact of school closure on households is critical when developing guidelines to prevent spread of pandemic influenza. A New York City survey conducted in June 2009 in 554 households affected by the 2009 pandemic influenza H1N1–related school closures showed that, during closure, 30% of students visited at least 1 locale outside their homes. If all the adults in the home were employed, an ill child was less likely to leave home. In 17% of the households, at least 1 adult missed some work because of the closure. If all adults in the home were employed, someone was more likely to take time off work. If other children were in the household, it was less likely that an adult took time off work. The findings of our study will be important when developing future pandemic school-closure guidance.

On 23 April 2009, an outbreak of a novel strain of pandemic influenza A (H1N1) (pH1N1) was identified in a New York City high school[1, 2]. This strain spread quickly throughout the city. In spring 2009 (schools were closed from the end of April through the end of June), and 57 schools in NYC were closed [3] for 5–7 days because high numbers of children were identified with influenza-like illnesses (ILI) (Influenza-like illness is an illness presenting as a fever and either a cough or sore throat.) [4]. School closure has been promoted as a nonpharmacological intervention that can mitigate the impact of an influenza pandemic [5]. However, the costs and potential benefits of such an intervention have not been fully studied [6, 7]. We measured the extent to which children stayed isolated, thus potentially slowing disease transmission during the closure, and the extent to which household inhabitants missed work because of the closure.

## METHODS

We conducted a telephone survey among households whose children attended 1 of 7 public elementary schools closed during the first week of June 2009 in response to outbreaks of pH1N1. The survey asked adult respondents if the student had an ILI in the week before or during the closure, if someone had to take time off from work to look after the child, what the primary location of the child was during the closure, and whether the child left the primary location at all during the school closure and if so, where he or she went. The survey also collected information regarding household composition, employment, and income.

We used an online survey platform (mrInterview) to administer the survey, which were made available in 3 languages: English, Spanish, and Mandarin. We made calls from the 11th to the 25th of June 2009. The New York City Department of Education provided a student roster for the 7 schools. Using this list, we identified and attempted to contact a total of 3,343 households with ≥1 children in the affected schools.

We conducted bivariate analyses comparing the health of the child (ILI) to each location visited, in order to identify any potential patterns. We also analyzed the data using the following general (logistic) regression models: 1) Was household time lost from work due to school closures? (no: 0, yes: 1); 2) were all adults in household employed? (no: 0, yes: 1); 3) what was the school grade of child (children) (kindergarten-fourth: 0, fifth-sixth: 1); 4) Did child (children) have ILI a week before or during closure? (no: 0, yes: 1); 5) Are other children in the home? (no: 0, yes: 1); What is the household income? (<$25,000: 0, ≥$25,000: 1).

Children left primary place of residence during closure (no: 0, yes: 1); = All adults in household employed (no: 0, yes: 1); school grade of child (kindergarten-fourth: 0, fifth-sixth: 1), child had ILI week before or during closure (no: 0, yes: 1); other children in home (no: 0, yes: 1); household income (<$25,000: 0, ≥$25,000: 1).

We ran 2 regression models for each of the above equations: one that included income as a predictor variable and one that did not include this variable (Table 3). We then converted the predictor values to probabilities (Table 2). We used Robust Huber/White standard error estimates to adjust for school-level clustering. Statistical analysis was performed using Stata, version 11.0 (StataCorp).

Table 1.

Characteristics of 554 households surveyed: School closures due to the 2009 pandemic H1N1 influenza A virus outbreaks, New York City, Spring 2009

 Variable (total, missing) No. % Grade of childa (550, 4) Pre-K to Fourth 472 86% Fifth 78 14% Child sick with ILI (551, 3) Ill with an influenza-like illnessb in the week before or during the school closure 308 56% Not sick with an influenza-like illnessb 243 44% Other children (554, 0) No additional children in household 206 37% At least one additional child in household 348 63% Income (303, 251) Less than $25,000 219 72% Greater than or equal to$25,000 84 28% Employment (554, 0) Households with at least one adult not employed 311 56% Households with all adults partially or fully employed 243 44% Time off work (521, 33) No one took time off work 433 83% At least one adult took some time off work due to closure 88 17% Visiting other venues (554, 0) Child did not leave the primary location during closure 389 70% The child left the primary location at least once during the closure 165 30%
 Variable (total, missing) No. % Grade of childa (550, 4) Pre-K to Fourth 472 86% Fifth 78 14% Child sick with ILI (551, 3) Ill with an influenza-like illnessb in the week before or during the school closure 308 56% Not sick with an influenza-like illnessb 243 44% Other children (554, 0) No additional children in household 206 37% At least one additional child in household 348 63% Income (303, 251) Less than $25,000 219 72% Greater than or equal to$25,000 84 28% Employment (554, 0) Households with at least one adult not employed 311 56% Households with all adults partially or fully employed 243 44% Time off work (521, 33) No one took time off work 433 83% At least one adult took some time off work due to closure 88 17% Visiting other venues (554, 0) Child did not leave the primary location during closure 389 70% The child left the primary location at least once during the closure 165 30%
a

Grade of child (a cut off at fifth grade was used, as there was a clear change in parental behavior with children in the fifth grades versus K - fourth grades, as opposed to a gradual change, when the variables were individually examined as dummy variables).

b

An influenza-like illness was defined as having a fever and either a cough or sore throat.

Table 2.

Probabilities of Time Lost from work and children leaving their primary residence during school closures due to the 2009 pandemic H1N1 influenza A virus outbreak: New York City, Spring, 2009a

 Household lost time from work due to school closuresc Children left primary residencea,d Including income (n = 290, R2 = .1090) Excluding income (n = 514, R2 = .1182) Including income (n = 299, R2 = .0331) Excluding income (n = 547, R2 = .0149) Variable Coef.b Robust Std. Error P Coef.b Robust Std. Error P Coef.b Robust Std. Error P Coef.b Robust Std. Error P Baselinee .11 .02 .00 .08 .01 .00 .40 .03 .36 .34 .02 .00 All adults in home employed .24 .03 .00 .25 .02 .00 −.14 .02 .02 −.10 .01 .00 Grade of child in school > 4th −.06 .02 .16 −.03 .01 .14 −.05 .01 .62 −.04 .01 .55 Child sick with ILIf .06 .01 .06 .04 .01 .27 −.08 .02 .32 −.06 .01 .08 Other children in household −.04 .01 .07 −.03 .01 .01 .01 .01 .88 .04 .01 .40 Household income ≥ $25,000 .02 .01 .52 −.10 .02 .25  Household lost time from work due to school closuresc Children left primary residencea,d Including income (n = 290, R2 = .1090) Excluding income (n = 514, R2 = .1182) Including income (n = 299, R2 = .0331) Excluding income (n = 547, R2 = .0149) Variable Coef.b Robust Std. Error P Coef.b Robust Std. Error P Coef.b Robust Std. Error P Coef.b Robust Std. Error P Baselinee .11 .02 .00 .08 .01 .00 .40 .03 .36 .34 .02 .00 All adults in home employed .24 .03 .00 .25 .02 .00 −.14 .02 .02 −.10 .01 .00 Grade of child in school > 4th −.06 .02 .16 −.03 .01 .14 −.05 .01 .62 −.04 .01 .55 Child sick with ILIf .06 .01 .06 .04 .01 .27 −.08 .02 .32 −.06 .01 .08 Other children in household −.04 .01 .07 −.03 .01 .01 .01 .01 .88 .04 .01 .40 Household income ≥$25,000 .02 .01 .52 −.10 .02 .25
a

The coefficients are expressed as probabilities of occurrence. Thus, the probability of a baseline household (see note above) losing time from work due to the school closures is 9% (.09). The impact of the other variables is relative to that probability. For example, having all adults in household employed increases the probability of work time lost by 33%, so that households with all adults employed have a 42% (9% + 33%) probability of reporting work time lost.

b

where , we calculated the coefficient by subtracting the difference between for each coefficient and the baseline (see Table 3 for the original values)

c

Logit (p (Household lost time from work due to school closures)) = Employment of adults + Grade of child + Health of Child + Other children in home + Income

d

Logit (p (Children leave primary location)) = Employment of adults + Grade of child + Health of Child + Other children in home + Income

e

The baseline (constant) represents a home where at least one adult is not employed and the income is less than $25,000, with an only child in the home who is in kindergarten through fourth grade and who did not have an influenza-like illness before or during school closure. f ILI = influenza-like illness, defined as having a fever and either a cough or sore throat. Table 3. Logistic models (original values) of time lost from work and children leaving their primary residence during school closures due to the 2009 pandemic H1N1 influenza A virus outbreak: New York City, Spring, 2009  Household lost time from work due to school closuresa Children left primary residenceb Including income (n = 290, R2 = .1090) Excluding income (n = 514, R2 = .1182) Including income (n = 299, R2 = .0331) Excluding income (n = 547, R2 = .0149) Variable Coef Robust Std. Error P Coef Robust Std. Error P Coef. Robust Std. Error P Coef. Robust Std. Error P Baselinec −2.10 .28 .00 −2.42 .22 .00 −.40 .43 .36 −.65 .20 .00 All adults in home employed 1.49 .28 .00 1.72 .33 .00 −.66 .27 .02 −.48 .12 .00 Grade of child in school >4th −.92 .65 .16 −.58 .39 .14 −.20 .41 .62 −.18 .30 .55 Child sick with ILId .48 .25 .06 .46 .41 .27 −.33 .33 .32 −.26 .15 .08 Other children in household −.47 .26 .07 −.46 .18 .01 .05 .34 .88 .19 .23 .40 Household income ≥$25,000 .15 .23 .52 −.46 .40 .25
 Household lost time from work due to school closuresa Children left primary residenceb Including income (n = 290, R2 = .1090) Excluding income (n = 514, R2 = .1182) Including income (n = 299, R2 = .0331) Excluding income (n = 547, R2 = .0149) Variable Coef Robust Std. Error P Coef Robust Std. Error P Coef. Robust Std. Error P Coef. Robust Std. Error P Baselinec −2.10 .28 .00 −2.42 .22 .00 −.40 .43 .36 −.65 .20 .00 All adults in home employed 1.49 .28 .00 1.72 .33 .00 −.66 .27 .02 −.48 .12 .00 Grade of child in school >4th −.92 .65 .16 −.58 .39 .14 −.20 .41 .62 −.18 .30 .55 Child sick with ILId .48 .25 .06 .46 .41 .27 −.33 .33 .32 −.26 .15 .08 Other children in household −.47 .26 .07 −.46 .18 .01 .05 .34 .88 .19 .23 .40 Household income ≥ $25,000 .15 .23 .52 −.46 .40 .25 a Logit (p (Household lost time from work due to school closures)) = Employment of adults + Grade of child + Health of Child + Other children in home + Income. b Logit (p (Children left primary location)) = Employment of adults + Grade of child + Health of Child + Other children in home + Income. c The baseline (constant) represents a home in which at least one adult is not employed and income is less than$25,000, where there is a child in kindergarten through fourth grade who is an only child in the home and who did not have an influenza-like illness before or during the school closure.

d

ILI, influenza-like illness, defined as having a fever and either a cough or sore throat.

## RESULTS

### Response Rate

Of the 3,343 households, surveyors attempted to call each of these households at least once. A total of 1,034 (31%) of the households were successfully contacted. Of those, 587 (56.8%) agreed to participate; 554 completed the survey.

### Location of Children During School Closure

Most students claimed that their home was their primary location during the full closure (72%). During school closure, 30% of children left their primary location at some point, with the most common locale being a playground (Figure 1). A baseline household had a 34% probability of a child visiting any other venue. If all adults were employed, the probability of children leaving the home decreased by 10% , to 24% (Table 2). We ran the regression with and without (not shown) playground visits due to concerns that an outdoor environment was very different than going to an indoor environment. However, except for 2 children, all children who visited a playground also visited an indoor environment other than their primary locale; therefore, the results of the 2 analyses are nearly identical.

Figure 1.

Percentage of school children visiting locations during the weekdays when schools were closed due to outbreaks of 2009 pandemic H1N1 influenza A virus outbreaks:New York City, Spring, 2009.

Figure 1.

Percentage of school children visiting locations during the weekdays when schools were closed due to outbreaks of 2009 pandemic H1N1 influenza A virus outbreaks:New York City, Spring, 2009.

## DISCUSSION

Compared with similar studies in suburban and rural settings (ie, North Carolina in 2006 and Pennsylvania in 2009), we found that 40%–59% fewer households in New York City reported their children going outside the home during the school closure [8, 9]. This may reflect differences among urban, suburban, or rural households. However, it may also suggest that school closures may be more effective in isolating children in urban areas. The findings on lost work time are similar to the study in Pennsylvania [9]. In both cases, the majority of households reported no lost time from work because of the school closures. This is not surprising, as more than half of the households surveyed had at least 1 nonworking adult at both locales. As expected, those households where all adults worked outside the home had a higher probability of reporting time lost from work.

Many models and studies have examined the impact of school closures on a pandemic [12–24]. However, we found only a handful of studies that examined this issue from the household perspective [8, 9, 25–27]. This study provides insights on how urban households respond to school closure. Results from this, as well as other studies (eg North Carolina and Pennsylvania studies [8, 9]), should be used to update the models to determine a more realistic estimate of school closure costs to the household. This is critical to policy planning, as preliminary data have shown that school outbreaks have accounted for 16% of the cases of pH1N1 in the United States [28]. Because the effectiveness of this intervention continues to be debated, we hope that these data will help public health decision makers, school officials, and parents of school children evaluate the costs and benefits of future school closures as a means to manage epidemics in a community.

We thank the New York City Department of Education, for its tremendous assistance and cooperation, as well as Shane Grebel and his team for their data collection support.

Financial support. This information was collected and paid for by CDC; it was cleared by the human subjects’ board as a public health, non-research study to assess an existing public health intervention in response to an immediate public health threat.

Supplement Sponsorship. Published as part of a supplement entitled “The 2009 H1N1 Influenza Pandemic: Field and Epidemiologic Investigations,” sponsored by the Centers for Disease Control and Prevention.

Potential conflicts of interest. All authors: none reported.

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## Author notes

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.