A systematic review on outbreaks of COVID-19 among children within households in the European region

Objectives This systematic review aims to identify the secondary attack rates (SAR) to adults and other children when children are the index cases within household settings. Methods This literature review assessed European-based studies published in Medline and Embase between January 2020 and January 2022 that assessed the secondary transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within household settings. The inclusion criteria were based on the PEO framework (P-Population, E-Exposure, O-Outcome) for systematic reviews. Thus, the study population was restricted to humans within the household setting in Europe (population), in contact with pediatric index cases 1–17 years old (exposure) that led to the transmission of SARS-CoV-2 reported as either a SAR or the probability of onward infection (outcome). Results Of 1,819 studies originally identified, 25 met the inclusion criteria. Overall, the SAR ranged from 13% to 75% in 23 studies, while there was no evidence of secondary transmission from children to other household members in two studies. Evidence indicated that asymptomatic SARS-CoV-2 index cases also have a lower SAR than those with symptoms and that younger children may have a lower SAR than adolescents (>12 years old) within household settings. Conclusions SARS-CoV-2 secondary transmission from paediatric index cases ranged from 0% to 75%, within household settings between January 2020 and January 2022, with differences noted by age and by symptomatic/asymptomatic status of the index case. Given the anticipated endemic circulation of SARS-CoV-2, continued monitoring and assessment of household transmission is necessary. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This report was commissioned by the European Centre for Disease Prevention and Control (ECDC) to the PREP-EU Consortium, coordinated by Dr Constantine Vardavas (School of Medicine, University of Crete) under Framework contract ECDC/2019/001 Lot 1B. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data sharing is not applicable as no datasets were generated and/or analysed for this study.