A new study confirms that, compared to earlier versions of the SARS-CoV-2 virus, the omicron variant causes less severe disease in mice and hamsters, which are reliable models for understanding COVID-19.

In a study published in Nature on May 16, a research team led by University of Wisconsin–Madison virologist Yoshihiro Kawaoka and colleagues in Japan show that the BA.2 subvariant of omicron is similar to BA.1 in both the severity of illness it causes and in its ability to cause infection.