In-school COVID-19 transmission is rare—even among close school contacts of those who test positive for the virus—when schools heed public health precautions such as mandatory masking, social distancing and frequent hand-washing, according to results of a pilot study in Missouri aimed at identifying ways to keep elementary and secondary schools open and safe during the pandemic. A close contact is anyone who has been within 6 feet for more than 15 minutes in a 24-hour period with someone infected with COVID-19.