SARS-CoV-2 transmission in schools: An updated living systematic review (version 2; November 2020)

BACKGROUND: Better understanding of SARS-CoV-2 transmission risks is needed to support decision-making around mitigation measures for COVID-19 in schools. METHODS: We updated a living systematic review and meta-analysis to investigate the extent of SARS-CoV-2 transmission in schools. In this update we modified our inclusion criteria to include: 1) cohort studies; 2) cross-sectional studies that investigated and cross-assessed SARS-COV-2 positivity rates in schools and communities; and 3) pre-post studies. We performed risk of bias evaluation for all included studies using the Newcastle-Ottawa Scale (NOS). RESULTS: 6270 articles were retrieved and six new studies were added in this update. In total from the two updates and using the new inclusion criteria, we identified 11 cohort studies (1(st) update: n = 5; 2(nd) update: n = 6) and one cross-sectional study (1(st) update: n = 1; 2(nd) update: n = 0). We performed a meta-analysis on nine of the 11 cohort studies investigating IAR in schools. Nine cohort studies reported a total of 91 student and 52 staff index cases that exposed 5698 contacts with 101 secondary infections (overall infection attack rate (IAR) = 1.45%, 95% CI = 0.31%-3.26%). IARs for students and school staff were 1.66% (95% CI = 0.08%-4.78%) and 1.18% (95% CI = 0.00%-4.43%) respectively. The risk of bias was found to be high for most studies identified, limiting the confidence in results. CONCLUSIONS: There is limited high-quality evidence available to quantify the extent of SARS-CoV-2 transmission in schools or to compare it to community transmission. Emerging evidence suggests the overall IAR and SARS-CoV-2 positivity rate in school settings are low. Higher IAR were found in students, compared to staff. NOTE: This article is a living systematic review that will be updated to reflect emerging evidence. This is the second version of the original article published on 23 December 2020 (J Glob Health 2020;11:021104), and previous versions can be found as data supplements. When citing this paper please consider adding the version number and date of access for clarity.