key: cord-0890526-aj7nwbza authors: Suk, J. E.; Vardavas, C.; Nikitara, K.; Phalkey, R.; Leonardi-Bee, J.; Pharris, A.; Wiltshire, E.; Funk, T.; Ferland, L.; Bundle, N.; Semenza, J. C. title: The role of children in the transmission chain of SARS-CoV-2: a systematic review and update of current evidence date: 2020-11-09 journal: nan DOI: 10.1101/2020.11.06.20227264 sha: f2bb580b2c67b328d059289931d9c2b6178b7ddc doc_id: 890526 cord_uid: aj7nwbza Decisions on school closures and on safe schooling during the COVID-19 pandemic should be evidence-based. We conducted a systematic literature review to assess child-to-child and child-to-adult SARS-CoV-2 transmission and to characterise the potential role of school closures on community transmission. 1337 peer-reviewed articles published through August 31, 2020 were screened; 22 were included in this review. The literature appraised provides sufficient evidence that children can both be infected by and transmit SARS-CoV-2 in community, household and school settings. Transmission by children was most frequently documented in household settings, while examples of children as index cases in school settings were rare. Included studies suggested that school closures may help to reduce SARS-CoV-2 transmission, but the societal, economic, and educational impacts of prolonged school closures must be considered. In-school mitigation measures, alongside continuous surveillance and assessment of emerging evidence, will promote the protection and educational attainment of students and support the educational workforce. A total of 1411 studies were identified according to the specified selection criteria from 126 Medline and Embase. After the removal of duplicates, 1337 were screened by title/abstract, out 127 of which 102 were assessed via full text, and 22 studies subsequently included in this review. 135 Fourteen published studies were identified to address child-to-adult transmission of SARS-136 CoV-2. Two referred to transmission within a community setting, six within a household and 137 six within a school setting. Community settings 139 Only one case study and one ecological study assessed child-to-adult transmission of COVID- 140 19 within a community setting. A case study by Jung et al. (9) , reported the contact-tracing 141 results of a 9-year-old infected asymptomatic girl. A total of 1206 close and casual contacts 142 were identified of which 96% underwent a SARS-CoV-2 PCR test and for which the results 143 were negative for every close and casual contact, except for one adult. Goldstein & Lipsitch 144 (2020) (10) used data on COVID-19 cases in Germany evaluated the contributing role of 145 different age groups in COVID-19 community transmission. According to their analyses, 146 COVID-19 cases among 10-14 and 15-19 year olds were 0.78 times lower and 1. 14 (15) . An additional study from South Korea among 107 index children and 248 household 171 members, identified only one case of secondary transmission to a household member and the 172 secondary attack rate was estimated to be 0.5%. In this study an additional 40 confirmed cases 173 were found in household members, but it could not be determined as a secondary transmission 174 as they had the same exposure as the pediatric index case (16) . policies and testing rates) indicated that school closure was associated with a 62% reduction of 215 COVID-19 incidence per week and a 58% reduction in mortality per week. It was found that 216 countries which had a low cumulative COVID-19 incidence at the time of school closure, had 217 greater reductions in incidence and mortality compared to those with a higher cumulative 218 incidence at the same time. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint In our review, seven modelling studies assessed the role of school closure, and overall indicated that school closure is associated with a reduction in the number of cases, is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint Acknowledgments 278 We would like to thank Tommi Kärki and the ECDC team collecting data on COVID-19 response 279 measures for Figure 2 . We would like to thank Katerina Papathanasaki, Chrysa Chatzopoulou and 280 Ioanna Lagou for their assistance in data archiving and report preparation. We acknowledge the 281 bravery and dedication of educational professionals everywhere during these most challenging times. 282 This work was financed by ECDC under direct service contract ECD.10660. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint To estimate the impact on mortality attributable to the reduction of the U.S. healthcare labor force due to child-care responsibilities induced by school closure The reduction in healthcare workers due to school closures must not raise the mortality per case to more than 3·4% (2·7-4·2) or the elasticity of healthcare worker productivity must not exceed 0·099 (0·077-0·124) in order school closures to be effective. In the scenario that daily contacts are reduced by 60% a reduction in the peak of COVID-19 incidence by 24.4%, in the attack rate by 8.1% and in ICU admissions by 4.6% was estimated. In the scenario that daily contacts are reduced by 80% a reduction in the peak of COVID-19 incidence by 32.4%, in the attack rate by 11.8% and in ICU admissions by 5.5% was estimated. Auger et al. 2020 (29) USA Communitylevel, assessing the impact of school closure using population based data. To assess the impact of school closures on COVID-19 incidence and mortality. Data were collected for 6 weeks after school closure. School closure was associated with a significant decline in COVID-19 incidence. Relative reduction in COVID-19 incidence per week by 62% and a relative reduction in mortality per week by 58% is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint Figure 2 . Age-specific proportion of severe outcomes of COVID-19 in the periods up to, and after 1 September 2020, the European Surveillance System (TESSy) (data extracted 4 November, 2020 for the period up to 1 November 2020) . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted November 9, 2020. ; https://doi.org/10.1101/2020.11.06.20227264 doi: medRxiv preprint Download data on country response measures to COVID-19 2020 Susceptibility to SARS-CoV-2 Infection Among Children and Adolescents Compared With Adults: A Systematic Review and Meta-analysis An analysis of SARS-CoV-2 viral load by patient age Age-related differences in nasopharyngeal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) levels in patients with mild to moderate coronavirus disease 2019 (COVID-19) COVID-19 in children and adolescents in Europe: a multinational, multicentre cohort study Epidemiology of COVID-19 among children in China Frequency of Children vs Adults Carrying Severe Acute Respiratory Syndrome Coronavirus 2 Asymptomatically Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement South Korea: successful control by early detection and extensive contact tracing with testing Temporal rise in the proportion of younger adults and older adolescents among coronavirus disease (COVID-19) cases following the introduction of physical distancing measures Burden of illness in households with SARS-CoV-2 infected children The Role of Children in the Dynamics of Intra Family Coronavirus 2019 Spread in Densely Populated Area Transmission dynamics of SARS-CoV-2 within families with children in Greece: A study of 23 clusters Contact Tracing during Coronavirus Disease Outbreak, South Korea, 2020. 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