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 1.1 cohort studies (1st update: n=5;2nd update: n=6) and one cross-sectional study (1st update: n=1;2nd 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 TAR were found in students, compared to staff.