This research brief is one of a series of six briefs, which provide an overview of available evidence shown in the Campbell-UNICEF Mega-Map of the effectiveness of interventions to improve child wellbeing in low- and middle-income countries (LMICs), with this brief mapping the COVID-19-relevant studies. This brief provides an overview of the available evidence that may inform responses to the COVID-19 pandemic or that furthers the understanding of its impact on child well-being outcomes. This evidence may be directly related to policies to reduce COVID-19 transmission, such as closure of schools and colleges, personal protective equipment, movement restriction between borders and social distancing, or studies of interventions responding to the immediate socio-economic impacts, such as social protection measures, educational programmes and tele-health. The purpose of the research brief is to: (1) Make potential users aware of the map and its contents; (2) Identify areas in which there is ample evidence to guide policy and practice, and so encourage policymakers and practitioners to use the map as a way to access rigorous studies of effectiveness; and (3) Identify gaps in the evidence base, and so encourage research commissioners to commission studies to fill these evidence gaps. [This brief is an update of the 2020 version. It was written with assistance from Yashika Kanojia.]