key: cord-1050897-em6zooye authors: Haag, L.; Blankenburg, J.; Unrath, M.; Grabietz, J.; Kahre, E.; Galow, L.; Schneider, J.; Dalpke, A.; Lueck, C.; Buettner, L.; Armann, J. P. title: Prevalence and Transmission of SARS-CoV-2 in Childcare Facilities: A Longitudinal Study date: 2021-04-18 journal: nan DOI: 10.1101/2021.04.16.21255616 sha: 3ed49d801dfa176d724063c525fc179ea739675b doc_id: 1050897 cord_uid: em6zooye Objectives Previous data indicate that children might play a less crucial role in SARS-CoV-2 transmission than initially assumed. We conducted a study to gain further knowledge on prevalence, transmission and spread of SARS-CoV-2 among preschool children, their parents and caretakers. Study design Children, their parents and care givers in 14 childcare facilities in Dresden, Saxony/ Germany were invited to participate in the KiTaCoviDD19-study between July 2020 and January 2021. Seroprevalence of SARS-CoV-2 antibodies was assessed up to 4 times during the study period in all participating adults and personal characteristics as well as epidemiological information of personal SARS-CoV-2 history were obtained. Stool viral shedding of SARS-CoV-2 was analyzed every 2-4 weeks in all participating children. Results 318 children, 299 parents and 233 childcare workers were enrolled. By January 2021 11% of the participating adults were detected seropositive, whereas the rate of SARS-CoV-2 positive children was 6.8%. Overall, we detected 17 children with SARS-Cov-2 viral shedding in 8 different childcare facilities. In 4 institutions there occurred a maximum of three connected cases in children. About 50% of SARS-CoV-2 infections in children could not be connected to a secondary case within our study population. Conclusion This study could not provide evidence for a relevant asymptomatic (silent) spread of SARS-CoV-2 in childcare facilities, neither in a low nor a high prevalence setting. This finding adds to the evidence that childcare and educational settings do not play a crucial role in driving the SARS-CoV-2 pandemic. Since the Beginning of COVID-19 pandemic 1 school and childcare closures are one of the main strategies to limit transmission. These measures are based on the assumption that children play a similar role in transmitting SARS-CoV-2 as they do in transmitting influenza and that schools and childcare facilities closures effectively lower the overall transmission rate 2 . However, most countries, including Germany, report a much lower proportion of cases in children compared to their population size [3] [4] [5] . In addition, COVID-19 mostly leads to no or mild symptoms in children and presents a low risk of a serious course of disease to children, whereas the impact of school closures and limited social interactions on children's mental health is becoming increasingly apparent 6, 7 . While several studies in the UK and Norway could only identify a very limited spread of COVID-19 in primary and secondary schools 8,9 similar Individuals with a confirmed SARS-CoV infection, close contact to an infected individual or . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint individuals with respiratory symptoms with or without fever were not allowed to attend daycare facilities during the study period Children, their parents and childcare workers in 14 childcare facilities in Dresden, Saxony/ Germany were invited to participate in the KiTaCoviDD19-study. After informed consent, 5 mL of peripheral venous blood were collected from adult participants and serological testing for IgG-antibodies against SARS-CoV-2 was conducted. Parents were asked to collect stool samples from their children every two weeks. Excretion of SARS-CoV2, as mostly non-infectious particle, is known to occur in infected people, especially children, for at least two weeks 10 . This was used as an easy-to-obtain specimen in the childcare population. These stool samples were tested by PCR to detect stool excretion of SARS-CoV-2 RNA. All blood and stool samples were collected between July 2020 and January 2021. In addition, data on age, household size, comorbidities, regular medication and previously diagnosed SARS-CoV-2 infections in participants or their household contacts quarantine episodes, utilization of daycare during lockdown, number of contacts other than householdcontacts and the occurrence of respiratory symptoms were collected. Stool samples were frozen at -80°C and were thawed earliest after 4 weeks of storage. According to study protocol, initially, every second stool sample was examined. If at least one . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 18, 2021. ; stool sample within one childcare facility tested positive, all samples from this institution collected two weeks earlier and later were tested as well. The liquid handling system MicroLab Nimbus (Seegene, Duesseldorf, Germany) was used for nucleic acid extraction using a modified protocol supplied by the manufacturer (spatula point of stool in 1ml of ASL buffer, Qiagen/ mixed thoroughly and incubated for at least 10min/ centrifuged at 16.060g for 2 min/ supernatant was used for extraction procedure) as well as for PCR setup. Extraction was followed by real time reverse transcriptase polymerase chain reaction (RT-PCR) using Seegene's Allplex TM 2019-nCoV assay. This assay detects three target regions within the genome of SARS-CoV-2, namely the E gene, RdRP gene and N gene. The automatic calculation software supplied by Seegene was used for interpretation of the results. A specimen was considered positive in case of at least one detected target region. In each test series a stool specimen from a patient with confirmed SARS-CoV-2 infection was run in parallel as a positive control for correct extraction and PCR procedure. In case of test inhibition (internal control) the assay was repeated once. Blood samples were assessed for SARS-CoV-2 IgG antibodies using a commercially available chemiluminescence immunoassay (CLIA) technology for the quantitative determination of anti-S1 and anti-S2 specific IgG antibodies to SARS-CoV-2 (Diasorin LIAISON® SARS-CoV-2 S1/S2 IgG Assay). Antibody levels > 15.0 AU/ml were considered positive and levels between 12.0 and 15.0 AU/ml were considered equivocal. All samples with a positive or equivocal LIAISON® test result, as well as all samples from participants with a PCR-confirmed SARS-CoV-2 infection, were tested with two additional serological tests (chemiluminescent microparticle immunoassay (CMIA) intended for the qualitative detection of IgG antibodies to the nucleocapsid protein of SARS-CoV-2 (Abbott Diagnostics® ARCHITECT SARS-CoV-2 IgG ) and an ELISA detecting IgG against the S1 domain of the SARS-CoV-2 spike protein (Euroimmun® Anti-SARS-CoV-2 ELISA)). . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint Participants with detectable antibodies in at least two assays were considered seropositive. The study period was divided into a low-prevalence phase (July 15 th , 2020 -November 15 th , 2020) in which cumulative reported cases tripled in Dresden and a high-prevalence phase (November 16 th , 2020 -January 31 st , 2021) in which cumulative cases increased more than . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. The KitaCoviDD19-study which was approved by the Ethics Committee of the Technische Universität (TU) Dresden (BO-EK-180052020), registered on July 15 th , 2020 and assigned the clinical trial number DRKS00022729. At baseline, none of the participants were SARS-CoV-2 seropositive. In the low-prevalence phase until mid-November 2 study participants, one childcare worker (1/154 -0.7%) and one . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint parent (1/196 -0.5%) became seropositive. Both participants reported a known PCRconfirmed infection. They did not attend the same childcare facility. During the same period, we detected 2 positive stool samples, resulting in a cumulative prevalence of 2 out of 232 children (0.9%) SARS-CoV-2 positive children (table 3) . These children attended different childcare facilities. One case was not previously detected, however there was no epidemiological linked case in the same institution. The other child was symptomatic and SARS-CoV-2 infection was detected by PCR at that time. One epidemiological linked case occurred in the same institution. In both cases, the parents did not have detectable antibodies, nor did they report positive PCR-testing for SARS-CoV-2. At the end of January 2021 -after the second wave of the pandemic -25 out of 236 (10.6%) parents and 23 out of 187 (12.3%) childcare workers were seropositive (table 3) . The difference between the two groups showed no statistical significance (p=0.64). Seroprevalence in parents whose children remained in emergency care during the strict lockdown was significantly higher (12/64 (18.8%)) than parents whose children did not visit the facility during this time (13/152 (8.6%); p=0.038). Seroprevalence in childcare workers assigned mainly administrative was significantly higher (10/48 (20.8%)) than those with was not significantly between children attending emergency care and those who did not (4/64 (6.3%) vs 13/152 (8.6%); p=0.78). The The rate of seropositive participants during the low-prevalence phase following the first wave in the Federal State of Saxony/Germany was very low, with only 2 detected cases. Both of . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint these participants previously knew of their infections, quarantine warranties were issued accordingly, and we could not find connected cases to either participant. This supports the assumption that the current testing and quarantine methods in Germany during a lowprevalence phase were effective and could successfully prevent an undetected spread of SARS-CoV-2. In accordance, we could only find evidence for one undetected infection in a child during this period. Even though this child visited the childcare facility and no special hygiene or distancing measures were taken neither by the parents nor by the childcare workers, we did not detect a secondary case. The increasing SARS-CoV-2 cases during the second wave in the general population was mirrored in our study population. While the rate of seropositive participants rose considerably by January 2021, this increase was proportional to the increase within the general population in Dresden, Germany. The number of undetected infections detected only by antibody testing continued to be lower than previously assumed by some authors. (DOI: 10.1126/science.abb3221).We could not detect a significant difference between the rate of seropositive parents and childcare workers. The percentage of SARS-CoV-2 positive children within the high-prevalence study phase was considerably lower than the rate of seropositive adults. This finding is supported by previous studies that also reported lower infection rates in children 5, 12 . Over the whole study period, we detected a maximum of three connected cases in children, further strengthening the hypothesis that childcare facilities are not a major source of uncontrolled clusters 13 . Noteworthy as well was the fact that in two cases an infection among siblings was detected, in both cases the other sibling did not test positive in the corresponding stool samples. About 50% of SARS-CoV-2 infections in children could not be connected to a secondary case within our study population. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. ; While the rate of participating children only amounted to approximately 20%, we included an average of 72% of childcare workers. Due to this high participation rate, we are confident to have a reliable amount of samples analysed to evaluate the rate of SARS-CoV-2 infections among this group. We could not detect a significantly larger rate of infected childcare workers compared to the participating parents. While parents were significantly more often seropositive when their children visited the childcare facility during the lockdown period, this also implies a working environment without the possibility of home-office. This effect could therefore also be owed to the larger number of regular contacts within the work environment outside the household. This assumption is supported by the lower percentage of SARS-CoV-2 positive children in emergency care compared to those who stayed at home during the strict lockdown. The percentage of seropositive childcare workers whose infection was possibly connected to their childcare facility was considerably higher than among seropositive parents. Considering the fact that there was a significantly higher rate of seropositive childcare workers with mainly administrative duties compared to those without, the higher infection rate in childcare workers compared to children as well as the extremely limited spread linked to undetected SARS-CoV-2 positive children suggests that transmission between adults within the childcare facilities occurs more frequently than between children and adults. Therefore, hygiene and distancing measures between childcare workers themselves might be the key measures in these institutions and more important than between children and workers. There are several limitations to our study. We enrolled a limited number of participants in our study, thus it was possible that infections remained undetected. Moreover, a lower sensitivity of PCR-testing for SARS-CoV-2 in stool samples than in oro-and nasopharyngeal swaps might also contribute to underestimating the true numbers of infections 14 . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint However, the inclusion of low-as well as high-prevalence settings within the study period and the high participation rate of childcare workers in all facilities are strengths of our study. Additionally, the use of antibody testing instead of PCR testing reduces the possibility of missed undetected SARS-CoV-2 cases at least in parents and childcare workers. The study could not provide evidence for a relevant asymptomatic ("silent") spread of SARS-CoV-2 in childcare facilities, despite the lack of hygiene or distancing measures in this age group. In addition, adults seem to transmit SARS-CoV-2 more frequently than children. These findings add to the evidence that childcare and educational settings do not play a crucial role in driving the SARS-CoV-2 pandemic. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint Figure 2 : Positive SARS-CoV-2 infected children and the occurrence of epidemiological linked transmissions within the single participating childcare facilities (green -no epidemiological link detected, yellow -single cases without epidemiological link detected, orange -2 epidemiologically linked cases detected, red -outbreaks with > 2 epidemiologically linked cases detected, stopwatch -officially mandated quarantine by local health department during study period) . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted April 18, 2021. ; https://doi.org/10.1101/2021.04.16.21255616 doi: medRxiv preprint A Novel Coronavirus from Patients with Pneumonia in China Impact assessment of non-pharmaceutical interventions against coronavirus disease 2019 and influenza in Hong Kong: an observational study Coronavirus Disease 2019 in Children -United States Hospital admission in children and adolescents with covid-19 early results from a national survey conducted by the German society for pediatric infectious diseases (DGPI) Spread of SARS-CoV-2 in the Icelandic Population Rapid Systematic Review: The Impact of Social Isolation and Loneliness on the Mental Health of Children and Adolescents in the Context of COVID-19 Systematic review of COVID-19 in children shows milder cases and a better prognosis than adults Minimal transmission of SARS-CoV-2 from paediatric COVID-19 cases in primary schools SARS-CoV-2 infection and transmission in educational settings: a prospective, cross-sectional analysis of infection clusters and outbreaks in England Virological assessment of hospitalized patients with COVID-2019 The presence of SARS-CoV-2 RNA in the feces of COVID-19 patients Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland (SEROCoV-POP): a population-based study Transmission of SARS-CoV-2 in Australian educational settings: a prospective cohort study Prolonged presence of SARS-CoV-2 viral RNA in faecal samples nd serological testing, 3: 3 rd serological testing, 4: additional serological testing in December 2020) and reported numbers of SARS-CoV-2 infections in Dresden We thank R. Fischer for excellent technical support.