we retrospectively surveyed 128 students at a coeducational , state secondary school in an urban area of west midlands , uk , where attack rates for pandemic ( h1n1 ) 2009 were high and ( as of march 2010 ) levels of unemployment were among the highest in great britain ( 7 ) .
the head teacher selected 1 class from each of years 710 ( equivalent to us grades 69 , student ages 1115 years ) to participate .
the school had closed for 1 week in mid - june 2009 , reopened for 2 days , then closed for another week .
an electronic version of a similar questionnaire pilot tested at another school had been found comprehensible and acceptable to participants .
the london school of hygiene and tropical medicine ethics committee approved the study ; the health protection agency approved it as part of wider outbreak investigations not requiring additional approval .
students reported how many times they visited specified public places before the school closure and how many times they visited these places during closure ( children had been advised to not visit public places only if they were symptomatic ) .
students also provided information about persons who looked after them during closure . for typical school days before and during closure , students reported the number of different persons spoken to ( contacted ) in the following groups : contacts who attended their school ( contacts from the same class [ classmates ] , the same year but a different class [ yearmates ] , and the same school but a different year [ schoolmates ] ) and others ( age stratified to reflect the uk school system ) .
students were asked whether they were ill during closure and whether being ill affected their contact patterns .
approximately 100 students ( range 99103 , depending on place visited ) stated how frequently they would visit public places while school was open , and 46 stated how many times they visited these places during school closure ; 45 ( 98% ) of 46 visited > 1 place .
fewer students visited shops , places of worship , parks , and playing fields at least 1/week when school was closed than when open ( figure 1 ) . for other places ,
visits to public places during open and closure periods of a uk secondary school , june 
percentage of students visiting public places > 1/week while the school was open ( n = 99103 , depending on the place ) and while it was closed ( n = 46 ) .
numbers after bars show percentages in each group ; p values are from fisher exact tests comparing the proportions during the open versus closed periods . among those who provided information about caregivers , 93 ( 95% ) of 98
reported that > 1 adult looked after them during school closure ; 49% reported having 2 caregivers ( range 15 ) . among caregivers for whom further information was available , 125 ( 69% ) of 182
would have seen the student on a typical school day , 54 ( 31% ) of 173 typically worked outside the home , and 12 ( 34% ) of 35 took time off work to care for the student during school closure . among students , 73
provided number of contacts on a typical day during school closure ; 35 also provided information for a typical school day , and another 6 only provided information for a typical school day .
we therefore conducted unpaired and paired analyses on data from 79 and 35 respondents , respectively .
students who provided contact data were most likely to be in years 7 or 9 but were otherwise similar to those who did not .
the mean totals of reported contacts were 70.3 ( sd 40.8 ) and 24.8 ( sd 22.5 ) during typical school days and closure , respectively ( figure 2 ) .
school closure was therefore associated with a reduction of 45.5 ( 95% confidence interval [ ci ] 33.857.2 ) in students typical daily number of contacts , a 65% relative reduction ( 95% bootstrap ci 52%73% ) .
the corresponding absolute and relative reductions in numbers of contacts with other students were 37.0 ( 95% ci 27.046.9 ) and 65% ( 95% bootstrap ci 52%74% ) , respectively .
the absolute and relative reductions in the numbers of contacts made with adults ( including teachers ) were 8.5 ( 95% ci 4.912.1 ) and 63% ( 95% bootstrap ci 45%75% ) , respectively .
no apparent change was found for number of contacts with adults outside school ( 34% , 95% bootstrap ci 6% to 63% ) .
number of contacts made by students with persons in different categories and the changes associated with school closures .
a ) total contacts overall and with students and adults ; b ) contacts with persons in different categories at school and in different age groups outside school ; c ) absolute reductions in numbers of contacts with persons in different groups associated with school closure ; d ) relative reductions in numbers of contacts with persons in different groups associated with school closure . in ( a ) and ( b )
, large black markers indicate the mean number of contacts ; small gray markers indicate individual data points ; circles indicate data for when the school was open ( n = 41 ) , crosses indicate data for when the school was closed ( n = 73 ) . in ( c ) and
( d ) , error bars indicate 95% confidence intervals . the greatest reductions in the numbers of contacts were for students from the same school ( figure 2 ) , e.g. , 80% reduction in numbers of contacts with classmates and yearmates . absolute reductions in numbers of contacts with persons not attending the school were small ; the relative reductions had wide confidence intervals and rarely showed evidence of a genuine reduction ( figure 2 ) . paired analysis of data for 35 students with information for contacts during both periods produced similar results as unpaired analysis .
among 40 respondents who reported illness during closure and self - assessed whether they consequently contacted fewer persons , 53% stated that their contacts were reduced , 33% stated that they were not , and 15% were unsure .
closing this school was associated with a 65% reduction in face - to - face conversational contacts made by secondary school students , primarily because of reductions in contact with students from the same school .
our estimated reductions exceed estimates from analyses of surveillance data for seasonal influenza - like illness in france ( 24% reduction in child - to - child transmission during school holidays compared with in - school days ) ( 8) and a study conducted in belgium ( 19% reduction in total contacts made by children and adolescents during easter holidays ) ( 9 ) .
our estimate of a 65% reduction in total contacts is similar to that from a survey at a primary school in germany , in which students reported 72% fewer contacts on sundays than on weekdays but in which all classmates were considered contacts ( 10 ) .
consistent with findings of other studies ( 1113 ) , most students visited public places during closure , although certain places were visited less frequently while the school was closed than when open .
our definition of contact excluded nonconversational contacts ( e.g. , passengers on public transport ) , which may enable transmission , and some conversations may not involve close contact .
we did not collect data about duration or intensity of contact or whether persons were contacted multiple times .
for logistical reasons , a 23 week delay occurred between school reopening and completion of questionnaires , providing potential for recall bias and underestimation of numbers of contacts during school closure ( although closure was unusual ) .
prospective data collection was impossible and has limitations , including greater effort required from participants and therefore potentially lower response rates .
the data refer to a convenience sample from 1 secondary school during what was often perceived as a mild pandemic and may not be generalizable to other situations ( e.g. , primary schools , different socioeconomic settings , infections with high case - fatality rates , or different seasons ) .
most students provided data only for the closure period , and few did so for a typical school day ( probably because of the order of questions ) .
paired analysis of 35 students who provided data for both periods produced similar results to the unpaired analysis .
other issues must also be considered when deciding whether to close schools ( 14 ) .
subject to the limitations described above , reactive school closures may substantially reduce the numbers of contacts made by students and may potentially reduce transmission of infection in some settings .
 to determine how school closure for pandemic ( h1n1 ) 2009 affected students contact patterns , we conducted a retrospective questionnaire survey at a uk school 2 weeks after the school reopened . 
 school closure was associated with a 65% reduction in the mean total number of contacts for each student . 
The Study
Conclusions