To determine the effects of age and variants of concern on transmission of SARS-CoV-2, we analyzed infection rates among close contacts over 4 periods in Toyama Prefecture, Japan. Among household contacts, odds of infection were 6.2 times higher during the period of the Omicron variant than during previous periods, particularly among children and adolescents.
Keywords: 2019 novel coronavirus disease; COVID-19; Japan; SARS-CoV-2; contacts; coronavirus disease; household; infection rates; respiratory infections; severe acute respiratory syndrome coronavirus 2; transmission; variants of concern; viruses; zoonoses.