In a sign that scientists still don’t fully understand how some COVID-19 variants manage to evade the immune system, a new Ontario study has found that retirement- and long-term-care home residents infected during the first Omicron wave were 20 times more likely to get reinfected by the virus than those who avoided a prior infection.

The surprising finding by researchers at McMaster University runs counter to the prevailing wisdom that a previous COVID infection affords protection against future infections, at least in the older adults who participated in the study.