key: cord-0717702-qhpm46rt
authors: Bonaccorsi, Guglielmo; Paoli, Sonia; Biamonte, Massimiliano Alberto; Moscadelli, Andrea; Baggiani, Lorenzo; Nerattini, Marco; Lastrucci, Vieri; Zanobini, Patrizio; Lorini, Chiara
title: COVID-19 and schools: what is the risk of contagion? The results of an antigen rapid test-based screening campaign in Florence (Italy)
date: 2021-09-20
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2021.09.027
sha: a7a9f853e943d831b77d49c2401335798a801270
doc_id: 717702
cord_uid: qhpm46rt

Introduction in the COVID-19 era, the debate around the risk of contagion at school, is intense in Italy. The Department of Welfare and Wealth of Florence promoted a screening campaign with antigen rapid tests for all the students and school personnel. The aim of this study is to assess the SARS-Cov2 circulation in the school setting by means of a mass screening conducted in every primary and middle school of Florence. Methods All the students attending primary and middle schools of Florence and the school personnel were asked to take part. The campaign started on 16th November 2020 and was completed on 12th February 2021. If the antigen rapid test resulted positive, a molecular test was provided to confirm the result. Results 18,414 subjects were tested with 15,233 students (82.7%) and 3,181 members of the school personnel (17.3%). Only in 27 cases (0.15%) the rapid test gave a positive result. Moreover, only 14 of the 27 positive rapid tests were confirmed as positive by the molecular test. These results show a very low number of SARS-CoV-2 cases among the people tested (0.08% of the total). Conclusions These results show that the spread of SARS-CoV-2 infection at school, during the months of the screening and with the respect of strict preventive measures was low.

1-The debate on schools reopening during the pandemic in Italy is still strong 2-An antigen rapid test-based screening campaign was conducted 3-The results show an extremely low number of Sars-Cov-2 cases at schools. 4-A reopening strategy, although with preventive measures, is to be considered.

The World Health Organization (WHO) on March 11, 2020, has declared the novel coronavirus (COVID-19) outbreak a global pandemic [1] . Even before that moment, many countries had imposed restrictions on citizens to limit the spread of the virus. The main measures taken were the promotion of physical distancing, the closure of borders between different regions, the cancellation of public events and the closure of schools, universities, and other educational institutions. Italy was one of the first Western countries severely affected by the coronavirus pandemic and the Region of Tuscany has been mildly affected during the first wave [2] . In the Province of Prato, in May 2020, the seroprevalence of SARS-CoV-2 antibodies in a representative sample of health care workers, participants involved in essential support services and those who worked from home were 4.1%, 1.4% and 1.0%, respectively [3] . As part of the coronavirus disease With the reopening of the schools, several rules were introduced and adopted by students and school personnel, such as the mandatory use of facemasks, social distancing, minimal interaction between classes and staggered entrance times among different classes and schools. Moreover, any student or member of school personnel who had a fever over 37.5° C or presents any flu-like symptoms or any other symptoms consistent with COVID-19 was not allowed to go to school and had to be tested for SARS-CoV-2. In the case of a student resulting positive to SARS-CoV-2 the whole class had to be quarantined [5]. On 13 th November 2020 the Tuscany Region was declared a "red zone" and, according to the regulations of that period, not only high schools (for students aged [14] [15] [16] [17] [18] [19] but also the 2 nd and 3 rd middle schools (for students aged 12-13) were closed [6] .

Therefore, since about mid-November, only students from primary schools and from the 1 st middle schools (students aged 5-11) were attending classes at school. This situation lasted until 11 th January when Tuscany was declared a "yellow zone" [7] . After that, middle schools were fully reopened also for 2 nd and 3 rd classes, in addition to the students of 1 st classes, while high schools remained closed.

In order to keep schools safe, to monitor the spread of SARS-CoV-2 in the schools of Florence (Tuscany) and to evaluate the preventive measures adopted, the Department of Welfare and Health ("Assessorato al Welfare e sanità, accoglienza e integrazione") of the City of Florence promoted a mass screening with antigen rapid tests for all the students and school personnel who were asked to participate on a voluntary basis. The aim of this study is to assess the SARS-Cov2 circulation in the school setting by means of a mass screening, promoted by the City of Florence, conducted from November 2020 to February 2021 in every primary and middle school of Florence.

The mass screening, promoted by the Department of Welfare and Health ("Assessorato al Welfare e sanità, accoglienza e integrazione") of the City of Florence, involved every primary and middle school of the city. It started on 16 th November 2020 and was completed on 12 th February 2021. Participation in the screening was not mandatory either for students or for school personnel; only those who had previously presented the signed informed consent were allowed to participate in the screening and be tested. The informed consent for the students had to be signed by a parent or a legal guardian because they were minors. During the study period, several preventive measures were in place in schools, such as the mandatory use of facemasks, social distancing, minimal interaction between classes and staggered entrance times among different classes and schools. Moreover, any student or member of school personnel who presents any symptoms consistent with COVID-19 was not allowed to go to school and had to be tested for SARS-CoV-2. In the case of a student resulting positive to SARS-CoV-2 the whole class had to be quarantined [5] .

Therefore, during the screening period, some school classes were under quarantine after a previous finding of a case of SARS-CoV-2 infection and, as a consequence of this, those classes with a higher probability of having some cases of infection were not subjected to the screening process.

The screening was first conducted on the students who were attending 1 st middle schools. After that, the screening was continued with students from primary schools. Students from the 2 nd and 3 rd middle schools were involved in the screening after the reopening of schools for them on 11 th January 2021. Therefore, in summary, the screening of 1 st middle schools started on 16 th November 2020 and ended on 3 rd December 2020, the screening of primary schools started on 4 th December 2020 and ended on 12 th February 2021, the screening of 2 nd and 3 rd middle schools started on 11 th January 2021 and ended on 9 th February 2021. Every time the students of a school were tested, the members (teachers and all other kinds of workers) of school personnel who were working that day were tested as well. Consequently, since some teachers or other workers work in more than one school and since middle schools were involved in the screening on at least two different dates (1 st middle schools were tested in November and December, 2 nd and 3 rd middle schools were tested in January and February), some members of the school personnel were tested twice.

Tests were performed with antigen rapid tests for SARS-CoV-2 by teams composed of medical doctors and nurses. The organization and the implementation of the screening at the schools were managed by medical doctors residents in Hygiene and Preventive Medicine at the University of Florence and by some members of the Department of Welfare and Health ("Assessorato al Welfare e sanità, accoglienza e integrazione") of the City of Florence. All the members of the teamwork described above worked together on drafting the protocol in advance, before the beginning of the screening campaign, in order to have a standardized process of testing and isolation shared and approved by all the subjects who were to take part of the project. The protocol together with the date of testing was communicated to the Directors of each school well in advance in order to give enough time to prepare the school personnel and collect the signed informed contents, which had been previously provided to families.

The place in the school where tests were performed was decided by the Directors of the schools and was approved by the public health physicians present at the time. Most of the time the chosen place was the school gym since it was the most spacious area available. Different classes were tested one at a time and all the students from each class were asked to wait 15 minutes, before going back to their classroom, after the last student of the class had been tested. The waiting period took place in spacious selected areas or rooms where the students and members of the school personnel could keep a suitable distance from each other. Members of the school personnel were tested after the screening on the students had been concluded. Moreover, the name of every student tested was written on their own test and a selected member of the school personnel was in charge of taking a photo of each test 15 minutes after it had been carried out using a smart device provided by the Director of the school. In this way photos of every test carried out were saved and stored by the school Directors.

The enrolled people were tested with the "Coronavirus Ag Rapid Test Cassette (Swab)". It is an in vitro immunochromatographic assay for the qualitative detection of nucleocapsid protein antigen from SARS-CoV-2 in nasopharyngeal (NP) swab specimens directly or after the swabs have been added to viral transport media from individuals who are suspected of COVID- 19 [8] . In all cases it was ascertained that the test was valid (according to the package insert of the swab) and, in case of invalid test, it was repeated.

Every time a test resulted positive in these 15 minutes, it was checked by the other public health physicians present at the time and, if the positive result was confirmed, the person was immediately isolated in a specific previously selected room called the "COVID room". If the person who resulted positive was a student, the Director of the school was responsible for warning the parents of the student. In that case, the parents were asked to take the student to a selected Local Health Unit (Unità Sanitaria Locale) where the student was tested with a PCR (polymerase chain reaction) test for SARS-CoV-2 to confirm the result of the rapid antigen test. If the parents were not available at that time to come to the school, the student, after being isolated, was tested with a PCR-test in the "Covid room" by the healthcare workers present at the time and the test was taken to the laboratory to be examined. After that the student was asked to wait in the "Covid room" until their parents could come to take him home. When the person who resulted positive during the screening was an adult, he or she was asked to use a KN95, FFP2 or FFP3 mask and to go using his or her own means to the selected Local Health Unit where they would be tested with a PCR test. Every time an individual resulted positive after the PCR-test he/she was taken over by the authority of the prevention local unit in the same way as any other citizen who had resulted positive to SARS-CoV-2.

For the subjects who participated in the screening, in addition to personal data, information about the school, the class (in case of students), the date of the test, and its result were collected. This data was entered into an Excel TM database and made anonymous. After that, a descriptive analysis of the data was carried out. Data was presented as mean (Standard Deviation -SD) or percentage, as appropriate. The analysis was conducted using Microsoft Excel version 16.46 and Jamovi version 1.6.15.0 [9] .

The screening involved 75 schools from 24 comprehensive institutions ("comprensori scolastici").

In total, 18,414 subjects were tested with 15,233 students (82.7%) and 3,181 members of the school personnel (17.3%) ( Table 1 ). The screening test was offered to 21,515 students, therefore 6,282 (29.2%) students either were not at school on the day of the screening test or refused to participate in the study.

For some subjects, it was not possible to collect data such as sex, age or class attended.

Specifically, information regarding age was available for 13,469 students (1,764 missing values, equal to 11.6%) and for 2,101 members of the school personnel (1,080 missing values, equal to 34%).

Regarding sex, the data was missing for 2,140 (14.0%) students and for 558 (17.5%) subjects of the school personnel. For very few students (1.2%) the class which they attended was not available.

Of the 13,093 students for whom the information about sex was available, 52% (6,802) were male and 48% (6,291) female. As for the school personnel, 14% were male (368) and 86% were female (2.255) (Figure 1) .

The data relating to both sex and age was available for 85.9% of students (13,092 / 15,233) and for 65.3% of school personnel (2,077 / 3,181).

Almost all the students were aged between 6 and 14 and the average age was 10.0 years (SD 2.3).

The mean age of the school personnel was equal to 47.4 years (SD 10.5). Table 3 shows a distribution of the number of students by class.

The tests were performed in the period between November 2020 and February 2021. The two months of greatest activity were December and January when most of the student (76.3%) and

school personnel was tested (75.9%) ( Table 4) .

Almost all the executed tests were negative. Only in 27 cases, equal to 0.15% of the people tested, the swab gave a positive result. Moreover, only 14 of the 27 (48.1%) positive rapid tests were confirmed as positive by the molecular test. Figure 4 shows the results for the group of students and school personnel. The highest number of confirmed cases was identified in December: 6 cases of 14 were identified in this month. Four confirmed cases were identified in November, 3 in January and 1 in February.

The debate around COVID-19 pandemic is still intense: the reopening of restaurants and shops [10] , the balancing between economy and safety [11], the spread of fake news [12] , and the safely reopening of schools are some of the biggest challenges that governments are facing. This study confirms that, at least in the considered period, the circulation of SARS-CoV-2 among pupils of primary and secondary schools in Florence was quite low: 15,233 students, most of them aged between 6 and 14, and 3,181 members of the school personnel were tested through an antigen rapid test-based screening campaign, and a very low number of SARS-CoV-2 cases occurred among the tested people (0.08% of the total).

These findings let us consider a relatively low risk of being infected at school: in the district of the and researches that show a lower risk of infection at school. Other evidences from Italy show that, despite few cases of secondary infections occurred at schools, SARS-CoV-2 incidence among students was lower than in the general population [15] . According to a systematic review conducted in the UK, children and adolescents below the age of 20 have 44% lower odds of secondary infection, and this relationship is stronger in the age group between 10 and 14 years

[16]. Another U.S. study states that children are rarely an index case within family clusters of infection, although they certainly play a role in the transmission of the virus and have high viral loads even though they often are asymptomatic. [17] . Evidence of contact tracing data in China appears to show children becoming infected at a similar rate to adults within households but being less likely to become symptomatic [18] . However, subsequent data seems to demonstrate that children are less susceptible than adults to be infected with SARS-CoV-2. Other data from

China [19] demonstrates significantly lower odds ratios (ORs) of infection in children within households, confirmed by subsequent data from the Netherlands (including testing with serology) [20] .

In the screening campaign presented in this study, the cases of infection discovered are rare and they never represented a cluster distribution. The positive students may have been infected outside or in the family. Among school personnel there were very few cases as well, and this may be a sign that the likelihood of contracting the infection at school is low when the necessary hygienic rules (hand washing, social distancing, use of masks) and preventive strategies (not to allow symptomatic people to enter in the school and quarantine full classes after a finding of a case of infection) are respected. A study carried out in France shows that even among symptomatic children the transmission of the virus is low [21] , and a similar Irish research carried out before the closure of primary schools (before 12 March 2020) shows no evidence of infection among schoolchildren [22] . The same data comes out from a German study [23] , which also states that the closure of schools for long periods can have detrimental effects on the psychological wellbeing of the pupils. According to many papers, these similar results lead to the conclusion that closing schools do not produce an effective control of viral transmission, avoiding 2-4% of deaths, a much lower percentage than that one given by the implementation of social distancing and hygienic strategies (washing hands) [24] . Moreover, school closure carried out in Japan did not The present study has also some limitations. First, we have no data about the subjects who did not take part to the screening campaign; therefore, we could not exclude a selection bias. Second, inter-operator variability could have affected results of the study as test reading is user dependent and several different operators performed this task, even if all the operators who took part in the study were previously trained on reading the test. Lastly, there was no way of determining if there were false negatives.

In conclusion, our study places itself in the ongoing debate on Sars-CoV-2 and school reopening and closures, which is still a matter of discussion, and it will be useful to take decisions in the upcoming school year. 

The authors declare no conflicts of interest.

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